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Apps / PuTTY

PuTTY

SSH, Telnet and Rlogin client

Simon Tatham

uk.org.greenend.chiark.sgtatham.putty
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Putty is a SSH, Telnet & Rlogin client - this time for Linux.

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Screenshots

Putty configuration and console
Putty configuration and console

Observed history

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The initial import establishes a baseline. Future version changes will appear here.

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Upstream releases

Release notes supplied by the developer. These dates are not Flathub package publication times.

0.8516 Aug 2026
  • Security issue: fixed a remotely triggerable use-after-free in Pageant. (Might be exploitable to execute code, although this is not proved.)
  • Security issue: fixed a remotely triggerable buffer overflow if the OpenSSH encrypt-then-MAC cipher modes are in use. (However they are only used if a server supports nothing else.)
  • Security issue: fixed a buffer overflow in private key decryption, if the private key is constructed maliciously. (Only triggerable on purpose if you let somebody else generate your key for you.)
  • Denial-of-service security fixes: a server can trigger a tight loop in PuTTY, and even a MITM can make it consume unlimited memory at startup.
0.8422 May 2026
  • Security issue: fixed a remotely triggerable double-free in RSA key exchange. (We don't know of any way it is exploitable to execute code.)
  • Minor security issue: fixed a remotely triggerable crash in NIST ECDSA signature verification. (An assertion failure - definitely not exploitable to execute code.)
  • Minor security issue: fixed marking of Telnet and Rlogin session data with a trust sigil after you authenticated to a proxy (possibly allowing a server to spoof a repeat proxy password prompt).
  • Ability to run a specified command before starting the connection, e.g. to perform wake-on-LAN or a port knock.
  • On Unix: display 'pre-edit text', showing the progress of using multiple keystrokes to compose a single Unicode character.
  • On Unix: improved support for to running the GUI tools on Wayland (fixed startup issues and tuned performance).
  • Bug fix: configuring a SSH certificate authority on Unix would fail unless you manually made a config directory.
  • Bug fix: spurious "Network error: Socket is not connected" when authenticating to some HTTP proxies.
  • Bug fix: disabling cursor blinking in the Windows Control Panel but enabling it in PuTTY would lead to a tight loop.
0.838 Feb 2025
  • Support for ML-KEM, the NIST-standardised post-quantum key exchange mechanism. (In addition to NTRU Prime, which has been supported since 0.78.)
  • Support for full Unicode file names in Windows file selector dialogs. (However, these do not yet round-trip through a saved session.)
  • Bug fix: psftp -b works again.
  • Bug fix: assertion failure if an SSH connection times out at the login prompt.
  • Bug fix: crash in Pageant if an SSH connection is abandoned while waiting for a deferred decryption passphrase.
  • Bug fix: tight loop if PuTTY tried to send an empty answerback string.
  • Bug fix: accidental truncation of some configuration edit boxes' contents to 127 characters.
  • Bug fix: Windows XP support was accidentally broken, and now reinstated.
  • Bug fix: restored interoperation with third-party tools that auto-fill login prompts by sending ^M for Return.
  • Bug fix: confusion when terminal window resized by tools like FancyZones.
  • Bug fix: the small keypad keys didn't reliably work in the terminal on Unix.
0.8228 Nov 2024
  • Major refactoring of Unicode handling to allow the use of 'foreign' Unicode characters, i.e. outside the system's configured default character set / code page. Not yet complete, but the following things work:
  • Windows console: usernames and passwords entered interactively into PSCP, PSFTP and Plink can use foreign characters.
  • Windows command line: usernames, remote commands, and filenames entered via command-line options can use foreign characters.
  • PuTTY's own terminal (on Windows and Unix): even if it's not configured into UTF-8 mode for the main session, interactive usernames and passwords can use foreign characters.
  • Unicode version update: all character analysis is updated to Unicode 16.0.0.
  • Unicode terminal rendering: national and regional flags are now understood by PuTTY's terminal emulator. (However, correct display of those flags will depend on fonts and operating system.)
  • The Event Log mentions the local address and port number of the outgoing connection socket.
  • Bracketed paste mode can now be turned off in the Terminal > Features panel.
  • Unix Pageant: new --foreground mode for running as a subprocess.
  • Bug fix: the 'border width' configuration option is now honoured even when the window is maximised.
  • Bug fix: SHA-2 based RSA signatures are now sent with correct zero padding.
  • Bug fix: terminal wrap mishandling caused occasional incorrect redraws in curses-based applications.
  • Bug fix: Alt + function key in "Xterm 216+" mode sent a spurious extra escape character.