Bitvise SSH Server Version History  

For issues that might arise using the latest SSH Server versions, see Known issues.

Changes in Bitvise SSH Server 9.27:    [ 14 February 2023 ]

  • General:

    • Previous SSH Server 9.xx versions would incorrectly and unnecessarily allocate some thread-local storage indices for each connection, instead of at startup. This would effectively prevent the SSH Server from handling more than about 500 concurrent connections. Fixed.

  • Cryptography:

    • OpenSSL version updated to 1.1.1t. Bitvise software primarily uses Windows CNG for cryptography. We use OpenSSL for specific cryptographic algorithms not supported by Windows. Currently, these are chacha20-poly1305 and on older Windows versions, the elliptic curve secp256k1. Our software does not use OpenSSL features affected by recent OpenSSL security advisories.

  • Tasks and email notifications:

    • If more than one task was triggered by the same event, tasks could be removed from the execution queue which should not be removed, and the task that should have been removed would stay in the queue. Fixed.

    • The SSH Server would log an error when sending an email notification to multiple addresses that were duplicates of each other. Fixed.

  • File transfer:

    • When previous 9.xx versions upgraded settings from versions before 9.xx, the virtual filesystem mount point setting File sharing behavior was upgraded incorrectly. The correct behavior is to map the old Default value to Free, and the old Force value to Force. Instead, upgrading to 9.xx would change the old Default value to Force, and the old Force value to Use global defaults.

      This does not affect most users in a significant way since Free and Force behave the same for most clients. However, for users who previously changed mount point settings to force a specific file sharing mode, this oversight reset their custom file sharing settings to the new global defaults.

      This version fixes the issue for users who newly upgrade from a version before 9.xx. Users who already upgraded to a previous 9.xx version, and used the Force setting before upgrading, should check the new global file sharing settings in Advanced settings > File transfer to ensure these settings meet their requirements.

  • Control Panel and Settings:

    • When using the Log folder viewer to select and delete all log files, the SSH Server Control Panel would crash. Fixed.

    • Improved validation behavior for a number of field types in settings.

Changes in Bitvise SSH Server 9.26:    [ 16 January 2023 ]

  • EULA:

    • We updated our EULAs to formalize our existing practices regarding the nature and behavior of our software (it is a product, not a service; the data it handles is not sent to Bitvise; risk tradeoffs with updates) and the way we provide support (via email and our case management system, in written form).

  • Installation:

    • In previous versions, an automatic update would fail if the installer encounters an unexpected minor error. The SSH Server installation could be left inoperable, requiring the administrator to perform the update manually, if the installer e.g. could not create a shortcut.

      The SSH Server installer now treats specific conditions as warnings and continues if those non-critical conditions occur during an automatic update. Currently, these conditions include exit codes 105 (could not create shortcut) and 115 (could not configure authentication package). These now result in a warning exit code.

  • Cryptography:

    • OpenSSL version updated to 1.1.1s. Bitvise software primarily uses Windows CNG for cryptography. We use OpenSSL for specific cryptographic algorithms not supported by Windows. Currently, these are chacha20-poly1305 and on older Windows versions, the elliptic curve secp256k1.

  • General:

    • The SSH Server now runs auto-execute commands, such as the On-upload command, without creating a console window for each command. This dramatically increases the number of auto-execute commands that can run simultaneously. In previous versions, auto-execute commands would fail to start if approximately 100 were already running in the same Windows logon session.

    • If the SSH Server defines the environment variable USERPRINCIPALNAME, it now also adds environment variables USERPN_USERPART and USERPN_DOMAINPART. These contain the separate user and domain parts of USERPRINCIPALNAME.

  • File transfer:

    • The SSH Server's file transfer subsystem would exit with an exception, aborting the file transfer session, if the client tries to set a negative file time. If the SSH Server receives such file times, it will now continue the file transfer session, but will treat negative file times as invalid.

Changes in Bitvise SSH Server 9.25:    [ 30 October 2022 ]

  • Version information:

    • This version contains an upgrade access amnesty so it can be used with any license that is valid for a previous SSH Server 9.xx version. The minimum upgrade access expiry date to activate this version is January 1, 2022.

    • You can download this version here. (Alternative)

  • Security:

    • SSH Server versions 9.16 - 9.24 contain a flaw where, if settings are imported or upgraded from SSH Server versions 7.xx or 8.xx, some mount point types are not imported correctly. The incorrect import causes those mount points to grant unlimited filesystem access.

      The usual way to configure a mount point in SSH Server 7.xx/8.xx versions is to use the provider type FlowSfsWin. This is the default setting. Those mount points are upgraded correctly.

      However, it is possible to set mount point Provider type to Custom and configure Provider DLL to "FlowSfsWin". Users could configure this manually, or such a configuration could result after settings were imported from even older SSH Server versions, such as 6.xx.

      When SSH Server versions 9.16 - 9.24 import mount points of type Custom:FlowSfsWin from SSH Server versions 7.xx/8.xx, the setting Real root path is incorrectly ignored. This causes those mount points to grant unlimited filesystem access, where the mount point should be limited to a root directory.

      This version addresses this issue as follows:

      • Mount points with Provider type set to Custom now preserve the configured root path when upgraded or imported from SSH Server 7.xx/8.xx settings.

      • If settings were upgraded and saved by SSH Server versions 9.16 - 9.24, it is not possible to know if mount points of type Custom:FlowSfsWin that have an empty Custom root path were configured with unlimited access on purpose, or were upgraded incorrectly. Therefore, mount points of type Custom:FlowSfsWin with an empty Custom root path will now fail to initialize.

      • We provide a PowerShell script which you can run to identify mount points which require administrator attention.

        The script searches group and account settings entries in SSH Server settings. It displays mount points of type Custom:FlowSfsWin that have an empty Custom root path. If such mount points are found, then if you want the mount point to grant unlimited access, change Mount type to Unlimited access. Otherwise, change Mount type to Specific directory and configure a Real root path.

        This script can be run with any SSH Server 9.16+ version. It does not require updating to 9.25. If affected mount points are found, you can fix them without updating. This will address the issue, unless you import settings containing such mount points from 7.xx/8.xx versions again. Updating to 9.25 will ensure any future import works correctly.

  • Control Panel and Settings:

    • The Statistics tab now shows filtered text with a highlight.

Changes in Bitvise SSH Server 9.24:    [ 9 October 2022 ]

  • General:

    • Previous SSH Server 9.xx versions did not run on older Windows versions, such as Windows Server 2008 R2, unless KB 2533623 was installed. This version implements a workaround for this dependency, so that KB 2533623 is again not required.

  • Email:

    • The maximum length of the local part of an email address is now raised from 64 bytes to 128.

  • BvShell:

    • Improved inconsistent Tab auto-complete behavior.

    • The cd command now displays a warning when more than one parameter is passed. (In most shells, supplying more than one parameter to cd is invalid.)

  • Master/follower synchronization:

    • Fixed multiple issues associated with activation code synchronization.

    • The user interface in the follower now displays more clearly when the activation code could not be synchronized because master settings do not permit it.

  • Control Panel and Settings:

    • Settings entries, such as virtual groups and connect profiles, whose names are referenced by other settings entries, can now be renamed, so that references are automatically updated.

    • When editing an account settings entry in Easy settings, mount point settings (including permissions) would be reset on mount points, even if the mount points were not changed. Fixed.

    • Mount point permissions can now be configured in Easy settings.

    • CSV import for settings entries that contain nested lists would incorrectly fail to clear these lists when importing. Most significantly, importing a Windows account from CSV would fail to clear or overwrite a default "/" mount point inherited from the Everyone Windows group in Advanced settings. Fixed.

    • When starting a CSV import on a list that already contains entries, the interface now asks whether to clear existing entries before importing.

    • The Custom events interface can now display events filtered by name or description.

    • In SSH Server settings, a single press of the Alt key would block Alt+Tab and the Windows Key from working until the user switched windows using the mouse. Fixed.

    • Additional improvements to the behavior of the pop-up menu for the SSH Server Control Panel icon in the system notification area.

Changes in Bitvise SSH Server 9.23:    [ 5 June 2022 ]

  • Authentication:

    • On installations where all of the following is true:

      • Windows accounts can log in using password authentication.

      • Virtual accounts are in use and are backed by the automatically managed Windows account.

      • An account lockout policy is configured in Windows.

      In such configurations, it was possible for a remote attacker to lock out the automatically managed Windows account (usually BvSsh_VirtualUsers) by attempting password authentication against it. This would cause connections from virtual accounts to fail. If the SSH Server's automatic IP blocking is stricter than the Windows account lockout policy, the attacker could connect from multiple IP addresses to successfully lock the account.

      The automatically managed Windows account could also get locked out accidentally if its password expired, followed by many simultaneous connections from one or more virtual accounts. For example, this could occur with password expiry followed by 100 login attempts in the same second.

      The SSH Server now unlocks the automatically managed Windows account if it is locked out. If the password expires, the SSH Server now also takes steps to prevent a lockout due to other simultaneous logins.

    • Version 9.19 introduced the issue where passwordless authentication required a Windows restart in order to fully function after updating from a previous SSH Server version. Version 9.21 fixed this for updates from previous 9.xx versions, but this was not effective after updating from versions 8.xx. Fixed.

      Updating from versions older than 7.21 still always requires a Windows restart for passwordless authentication to fully function.

  • Email notifications:

    • When sending email through an outgoing SMTP server, the SSH Server now supports the SMTP authentication method AUTH LOGIN. This allows compatibility with servers such as

Changes in Bitvise SSH Server 9.22:    [ 31 May 2022 ]

  • In versions 9.19 and 9.21, it was not possible to create directories through virtual filesystem mount points that provide unlimited access. Fixed.

Changes in Bitvise SSH Server 9.21:    [ 30 May 2022 ]

  • Fixed an issue in version 9.19 where passwordless authentication required a Windows restart, or uninstallation and reinstallation followed by restart, in order to work after updating from a previous SSH Server version.

Changes in Bitvise SSH Server 9.19:    [ 28 May 2022 ]

  • Health monitoring:

    • On some systems, the Windows function GetSystemTimes can return inconsistent values. In this case, previous SSH Server 9.xx versions would stop due to an unexpected condition if the setting Health monitoring > Monitor CPU usage was enabled. Fixed.

    • In general, the SSH Server will no longer stop if one of the health monitoring features encounters an error, but will instead only log the error.

  • Control Panel and Settings:

    • Double-clicking the system tray icon for the SSH Server Control Panel would put the window into the foreground if it was hidden, but not if it was minimized, or behind other applications' windows. Fixed.

    • In the Custom events interface under Advanced settings > Logging, events are now sorted by default according to name, rather than number. Events can still easily be sorted by any column.

  • Email notifications:

    • In previous 9.xx versions, DKIM signing did not work. Fixed.

  • File transfer:

    • When the Real root path for a mount point did not exist, and the setting Create root path was disabled, the SSH Server would still create the directory if the client sent a "create directory" request. The SSH Server will no longer create the mount point root path in this circumstance.

    • For newly created mount points, the default value of the setting File sharing for uploads is now Delete instead of the previous value, Read, Delete. This is to prevent files from being read or copied in an inconsistent state by another application or connection while they are being uploaded.

  • Logging:

    • Further improvements to diagnostic logging for SFTP jump server mount points.

    • When logging the flags attribute for an auto-execute command, the Windows job object setting would be logged incorrectly. Fixed.

Changes in Bitvise SSH Server 9.18:    [ 5 May 2022 ]

  • Installation and update:

    • Improved reliability of creating temporary directories which could previously cause installation to fail.

  • Control Panel:

    • Fixed behavior of the pop-up menu when clicking the notification area icon.

    • Added support for Ctrl+A and Ctrl+Backspace key combinations in a variety of user interface elements that did not previously support them.

    • Addressed support for Esc and Tab keys in the Manage certificates dialog.

    • Fixed issue when deleting log files in the Log folder viewer.

    • In Easy settings, the Back and Next buttons were incorrectly swapped. Fixed.

  • Connections:

    • In previous 9.xx versions, the Connection timeout feature did not work. Fixed.

  • Tasks:

    • Configuring an On-logon command for an Execute command task would result in an error when running the task. Fixed.

    • Improved elevation handling for Windows sessions created for tasks.

  • SFTP jump server mount points:

    • Greatly improved diagnostic logging for connection issues when configuring Another SFTP server mount points.

    • Fixed an issue which would cause the SSH Server to emit an invalid SFTP packet when using Another SFTP server mount points. This would cause repeated connects and disconnects.

Changes in Bitvise SSH Server 9.17:    [ 12 March 2022 ]

  • Installation and update:

    • Due to a bug in the log utility included with SSH Server version 9.12, using built-in update functionality to update from version 9.12 to versions 9.14 and 9.16 would fail. Now, when updating from version 9.12, the first attempt will still fail, but will replace the log utility so that a second attempt succeeds.

      Running the new version installer directly to update manually works for all versions and does not trigger this issue.

    • When an SSH Server update was started automatically, but uninstallation of the existing version failed, the SSH Server would not automatically restart. When updating to future versions from version 9.17 or higher, if uninstallation fails but rollback succeeds, the main SSH Server service will now be restarted.

  • Settings:

    • When pasting from clipboard, password fields would accept ASCII control characters, including newline characters that are included by Excel when copy & pasting a selected cell. Password fields will now filter out control characters when pasting, including the Tab character.

  • SSH:

    • Improved detection of misconfigured obfuscation settings.

  • File transfer:

    • In previous versions including 8.xx, if an SCP client interrupted a download – such as by disconnecting – the SSH Server's SCP subsystem would still completely read the file and record a complete download in the I_SFS_TRANSFER_FILE event. Interrupted SCP downloads are now correctly logged as incomplete.

Changes in Bitvise SSH Server 9.16:    [ 14 February 2022 ]

  • Upgrade:

    • A major new feature in SSH Server 9.xx versions is the Windows session cache. This is enabled by default for new installations. When enabled, settings such as the On-logon command have a different effect than in previous SSH Server versions.

      To preserve behavior, the Windows session cache is now disabled when upgrading existing settings from versions 8.xx and earlier. This feature can be enabled or disabled in Advanced settings, under Sessions > Windows session sharing.

    • In versions 8.xx and earlier, it was possible to configure settings in subtly inconsistent ways. For example, it was possible to remove or rename a Connect profile so that the port forwarding settings in a group settings entry referenced a Connect profile which no longer exists.

      In previous 9.xx versions, the settings interface would not open after upgrading an installation which had settings configured this way. Fixed.

  • Control Panel and Settings:

    • When configuring an encrypted volume in Advanced settings, the setting Full path to data file now won't display an overwrite prompt when selecting an existing file.

    • Default settings in Tasks and actions now include straightforward examples for email notifications for uploads and downloads. These examples won't appear when updating from previous 9.xx versions unless the task list is reset to apply the new defaults.

    • The Log folder viewer now once again supports the Enter key to open the selected file.

  • Connections:

    • In previous 9.xx versions, the Connection on-logon command was broken and did not work. Fixed.

  • File transfer:

    • The Encrypted volume and Other SFTP server filesystem providers can now be configured to limit access to a subdirectory of the encrypted volume or remote SFTP filesystem.

    • Bitvise SSH Server provides access to filesystems which do not support POSIX permissions. In versions 8.xx and older, the SSH Server would respond to attempts to set POSIX permissions, such as using chmod, by simulating success. In previous 9.xx versions, the SSH Server would respond with failure if a client attempted to set only POSIX permissions, but not any supported attributes. This is a problem for scripts that assume chmod to succeed. The SSH Server will now once again simulate success for such requests.

    • If the feature Move completed uploads was configured in an account settings entry, as opposed to a group settings entry, the account would not be able to log in. Fixed.

    • The correct filesystem provider is now logged when an SFTP client attempts to use an invalid handle.

Changes in Bitvise SSH Server 9.14:    [ 23 January 2022 ]

  • Upgrade:

    • When upgrading from versions before 9.xx, the automatic log archival task is now disabled. This is to avoid interfering with any log maintenance the administrator has already set up.

    • If settings before 9.xx configured no limit to the number of simultaneous connections, such settings would be upgraded incorrectly to apply a lower limit. Fixed.

  • FTPS:

    • If the FTPS protocol is enabled, the SSH Server now supports TLS 1.3 on Windows versions where it is available. Currently, this requires Windows 11 or Windows Server 2022.

  • Tasks:

    • Log maintenance and command execution tasks now log an Info-level log event when they start.

    • Task triggers now support endsWith and contains as operators that work on strings. The contains operator also continues to work on structures, as it did previously.

  • Control Panel and Settings:

    • When configuring an encrypted volume in Advanced settings, the setting Full path to data file would have a misleading browse interface which did not allow selecting a filename which does not yet exist. Instead, a full path to a nonexistent file had to be entered manually. The browse interface now supports configuring a file which does not yet exist.

    • The Log Folder Viewer was not showing file icons in version 9.12. Fixed.

    • In the Statistics CSV export dialog, suggested filenames could include invalid characters. Fixed.

    • In account and group lists, reduced the number of columns for improved clarity and performance.

  • Command-line utilities:

    • The log utility did not work at all in version 9.12. Fixed.

New features in Bitvise SSH Server 9.12:    [ 1 January 2022 ]

  • Windows session cache: Multiple connections for the same user, either concurrent or consecutive, can now use the same Windows session. This can greatly improve reliability for clients that make frequent connections that access network shares.

  • Network share control: Settings now provide additional control over how network share connections are established where such connections could time out or occasionally fail.

  • Encrypted volumes: Clients can now access files which are encrypted at rest by the SSH Server. Concurrent users can access virtual filesystem mount points backed by one or more encrypted volumes. A volume is encrypted with a key configured in SSH Server settings.

  • SFTP jump server: Users can now access virtual filesystem mount points backed by a remote SFTP server to which the SSH Server connects on the user's behalf.

  • Tasks: The SSH Server can now run commands periodically, or triggered by configurable conditions based on recorded log events.

  • Email notifications: The SSH Server can now send email notifications triggered by configurable conditions based on recorded log events.

  • Log file maintenance: Automatic log file archival or deletion can now be configured as a scheduled task, without resorting to the Windows Task Scheduler.

  • Cryptography: New cryptographic algorithms include chacha20-poly1305 and encrypt-then-MAC hashing.

  • Improvements:

    • BvShell now supports the passwd command. This allows virtual accounts to change their password using a terminal shell that respects the SSH Server's virtual filesystem.

    • The SSH Server now consumes much less memory when using large settings that contain many accounts.

Known issues

  • Windows XP: All versions of our software that we recommend using are built using Visual Studio 2015. The C++ run-time library used by this Visual Studio version has a known issue where 1-2 kB of memory are leaked each time a new thread is created. This issue does not occur on later Windows versions; it does not occur e.g. on Windows Server 2003. Microsoft has stated they do not intend to fix this issue. Bitvise's view is that the impacts on our SSH Client and FlowSsh are manageable; whereas our SSH Server is rarely used on Windows XP. We therefore do not plan to work around this; but we warn that this can be a potential denial of service vector on Windows XP.

Older versions

Bitvise SSH Server 8.xx Version History

Bitvise SSH Server 7.xx Version History

Bitvise SSH Server 6.xx Version History

Bitvise SSH Server 5.xx Version History

WinSSHD 4.xx Version History

WinSSHD 3.xx Version History