PuTTY Known Bugs and Wish List

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This is the list of bugs that need fixing, and features that want adding, to PuTTY. The ‘pending’ list represents things that have not been done to the current development code; items marked as ‘fixed’ may not yet be in the latest release.

If you do not see a feature here, it's also worth checking the Changes page before mailing us to ask for the feature; it might already have been added.

There are other sites tracking bugs and feature requests in downstream packages of the Unix port, some of which undoubtedly apply to our code: Debian, Launchpad (us, Ubuntu), NetBSD.

Search the wishlist:

WWW www.chiark.greenend.org.uk

Here's an index of CVE numbers mentioned in our wishlist entries.

Recently fixed

These are items we believe we have addressed in a recent release. Not every change is documented here; see the Changes page for further information about what was in each release.

Fixed in pre-release builds of 0.83

• Bugs (and semi-bugs)
  • psftp-batch-files-broken: PSFTP batch files (-b option) broken on Windows
  • bare-wm-size-missing-conf-update: Windows: Change Settings didn't reflect window resizes from a bare WM_SIZE (e.g. FancyZones)
  • gtk-display-non-x: GTK pterm sets DISPLAY inappropriately under Wayland
  • gtk-small-keypad-ub: GTK: Alt could be ignored on small-keypad keys
  • lineedit-ctrlm-ctrlj: Ctrl-M and Ctrl-J weren't equivalent to pressing Return in terminal line editing
  • spurious-app-manifests: Spurious application manifests caused CLI tools to fail on XP
  • supdup-tdcrl-line-clear: SUPDUP: TDCRL operation should clear the new terminal line
  • userpass-state-assertion: term->userpass_state assertion when restarting a session that timed out in login
• Wishes
  • arm-dit: Arm: set PSTATE.DIT flag to protect constant-time cryptography
  • filereq-unicode: Windows: permit Unicode filenames in file requests
  • ml-kem: Implement the post-quantum ML-KEM key encapsulation method

Fixed in release 0.82

• Bugs (and semi-bugs)
  • maximised-window-border: Configured window border width ignored when maximised or fullscreen
  • rsa-sha2-padding: RSA signatures using SHA-2 hash lacked required padding
  • windows-stdio-prompts: Send Windows console tools' prompts directly to the console
  • x-bool-settings-ignored: Boolean settings specified via X resource / -xrm argument can be ignored
  • xterm216-altfn-escape: Alt + Fn in Xterm 216+ mode sent an unwanted prefix escape on Windows

Fixed in release 0.81

• Security vulnerabilities
  • vuln-p521-bias: NIST P521 private keys are exposed by biased signature generation

Fixed in release 0.80

• Security vulnerabilities
  • vuln-terrapin: Mitigations for SSH protocol 'Terrapin' vulnerability
• Bugs (and semi-bugs)
  • win-help-not-loaded-in-msi: Windows PuTTY as installed by the MSI can't find its help file

Fixed in release 0.79

• Bugs (and semi-bugs)
  • unix-bell-overload-timing-scale: Unix PuTTY misreads/writes bell overload timing settings
  • win-install-scope: PuTTY 0.78 Windows installer misbehaviour
  • unix-maximised-font-size-assertion-failure: GTK PuTTY can fail an assertion on changing the font size while maximised
  • unix-resize-assertion-failure: GTK PuTTY can fail an assertion on a server-controlled resize
  • win-server-resize-forbidden-hang: Windows: hang if server tries to resize window when resizing is forbidden
  • wrapping-edge-cases: Multiple edge-case bugs in terminal line wrapping
  • zipfile-missing-chm: putty.chm help file missing from putty.zip
• Wishes
  • hmac-sha2-512: Support for HMAC-SHA-512 in SSH-2
  • mouse-reporting-1003: Mouse reporting including plain mouse movements (type 1003)
  • mouse-reporting-horiz-scroll: Horizontal scroll action support in terminal mouse tracking

Fixed in older releases

See the historic wishlist page for information about issues fixed in older releases.

Outstanding issues

These are bugs still to be fixed and features remaining to be implemented.

Bugs

These items are clearly actual problems and we want them fixed.

• pscp-size-change: PSCP assertion failure if remote source file changes size
• win-jumplist-trouble: Trouble with Windows 'jump lists' of recently used sessions since 0.68
• win11-suspend: Terminal display updates stop happening after resuming from Windows 11 Modern Standby
• assert-fail-newsavelines: Failed assertion: count234(term->scrollback) <= newsavelines
• change-scrollback-altscr: Changing scrollback size when on alternate screen clears the screen
• exit-codes: Provide more useful exit codes
• fullscreen-taskbar: Switching to full-screen doesn't always hide taskbar
• keyboard-problems: Problems with various keyboard layouts / input methods
• pageant-load-fail: Pageant -c continues even if key load fails
• pscp-recursion-dest-dir: PSCP recursive copy to a new directory tries to copy all files over that dir
• puttygen-accel-bogosity: Bogosity with PuTTYgen keyboard accelerators and menu bar
• scrollbar-sub-message-loop: Dragging the Windows terminal scrollbar blocks handling of many non-GUI events
• ssh2-utf8-strings: SSH-2 message strings etc should be in UTF-8
• win-message-loop: Using modal dialog boxes on Windows invokes a substandard message loop

Semi-bugs

These are things which might be bugs or might not, depending on your precise definition of what a bug is.

• false-positive-malware: PuTTY is persistently misreported as malware
• store-vs-windows-s: PuTTY's Windows Store entry refuses to install in "S mode"
• async-dns: DNS lookups are synchronous.
• da-response: PuTTY's response to DA is suboptimal
• fxp-short-reads: Support short reads in SFTP
• portfwd-multi: Port forwarding should cope better with already-used ports
• psftp-speedups: Further speedups for PSFTP
• pterm-settings: pterm's relationship to saved sessions should be clarified
• serial-check-parity: Serial backends don't enable parity checking
• sgr21: PuTTY's interpretation of SGR 21 differs from Linux's
• ssh-rportfwd-addr-mismatch: Remote port forwarding fails due to address mismatch (Bitvise)
• unicode-select: Word-at-a-time selection configuration ignores Unicode
• win-pterm-line-wrap: pterm.exe handles line breaks badly on Windows 10
• win7-jumplist-duplicates: Windows "jump list" duplicates items between pinned and recent lists

Wishlist

These are things that have been requested by users or which seem to me like a good idea. Not all of these are likely to be implemented without outside help, and some of them will positively never be implemented.

Plausible features we hope to get round to adding at some point:

• "fun": Just needs tuits, and not many of them.
  • auth-pref: Preference order for authentications
  • autoscroll-accel: Auto-scrolling while selecting should have variable speed
  • character-line-delay: Configurable per-character and per-line delays
  • cmdline-licence: Command-line tools should have an option to display licence
  • cmdline-x-display: Command-line option to set local X display
  • command-hooks: Hooks to run external commands (e.g. after forwarding set up)
  • ctrl-pgupdn-config: Ctrl-PgUp and Ctrl-PgDn scrolling should be configurable
  • emacs-keys: Emacs cursor-key etc mappings
  • handle-unimplemented: Handle SSH2_MSG_UNIMPLEMENTED more usefully
  • menu-bar: Menu bar in the PuTTY window
  • meta-bit: Option to have Alt key set the meta bit
  • multi-font: Multiple font selections
  • pageant-logging: Logging for Pageant
  • pageant-wildcard: Accept wildcards on Pageant command line
  • passthru-default-printer: Pass-through printing: option to go with Windows default printer
  • proxy-iprange: Support for IP address ranges (x.x.x.x/y) in proxy exclude list
  • pscp-check-first: PSCP could check source filespec before connecting
  • pscp-filemodes: Control of file permissions in PSCP and PSFTP
  • pscp-stdout: Make PSCP optionally log to stdout instead of stderr
  • psftp-progress: Progress indication for PSFTP
  • startup-fullscreen: Option to start up in full screen mode
  • terminfo: Maintain a terminfo for PuTTY's terminal emulator
  • window-title-keywords: Variable expansion in configured window title
• "tricky": Needs many tuits.
  • avoid-msgbox: Avoid using message boxes for "connection closed" and friends
  • cmdline-any-option: Command-line general `-o Name=Value' type option
  • config-inheritance: Inheritance between saved sessions
  • config-locations: Store configuration in disk file, HKEY_ALL_USERS, other locations
  • dedicated-sharing-upstream: Separate dedicated utility to act as connection sharing upstream
  • do-text-splitting: Frontends need control over where do_paint() splits runs
  • i18n: Framework for internationalisation
  • key-mapping: Generic key mapping facility
  • log-mkdir: Create directories for log files automatically
  • many-sessions: Make life easier for people with lots of saved sessions
  • no-terminal-window: Ability to run without terminal window (for forwarding etc)
  • pageant-key-confirm: Option to require confirmation of key use in Pageant
  • pageant-timeout: Key timeout in Pageant
  • port-mac: Port to Mac OS X
  • portable-keyboard: Shared keyboard handler across platforms
  • proxy-logging: Log proxy connection setup etc
  • reorder-sessions: Allow frequently used saved sessions to be easy to access
  • right-alt: Support for Right Alt on keyboards which don't call it AltGr
  • save-scrollback: Allow saving scrollback to a file (logging formatted terminal output)
  • search-scrollback: Searching facilities in the scrollback
  • sftp-tilde: Accept home directories as "~" and "~username" in PSCP and PSFTP
  • ssh-url-scheme: Support for an "ssh" URL scheme
  • status-bar: Status bar on the PuTTY window
  • system-menu: Expansions to the System menu
  • unicode-mappings: Compatibility mappings for Unicode characters unsupported by a font
  • win-enum-serial-ports: Enumerate serial ("COM") ports on Windows
  • winrt: Port PuTTY to Windows RT (aka Metro)

Features we're not sure about, or which probably won't get added unless someone else does the hard work:

• "fun": Just needs tuits, and not many of them.
  • border-colour: Ability to configure border colour, when present
  • cmdline-edit-session: Command-line option to edit a session rather than launching it
  • cmdline-environ: Command line stored in environment variable
  • emulate-3-buttons: Make left+right click emulate middle-click, like XFree86
  • env-passthrough: Option to pass through certain environment variables
  • fore-back: Specify foreground and background colours separately
  • forwarding-unix-sockets-client: Port-forwarding using Unix-domain sockets on the client
  • forwarding-unix-sockets-server: Port-forwarding using Unix-domain sockets on the server
  • function-keys-8bit: Option to start key sequences with 0x9B instead of 0x1B
  • intel-keyboard: Keyboard mode to support Intel serial consoles
  • pageant-activity-ind: Visual/aural indication of Pageant activity
  • pageant-hibernate: Discard sensitive material in Pageant on hibernation
  • paste-on-release: PuTTY should paste when the paste button is released
  • portfwd-range: Allow port ranges in tunnel UI
  • psftp-paging: Paging on PSFTP directory listings
  • psftp-prompt: PSFTP should have a "prompt" command
  • reconnect-auto: Reconnect automatically if connection goes down
  • sel-colours: Make selection colours configurable
  • sgr-as-colours: Be able to change text colour or font in response to SGR Bold, Underline etc
  • ssh2-openssh-certkey-fallback: Automatic fallback from certified to uncertified SSH keys during userauth
  • ssh2-openssh-certkey-fallback-pageant: Pageant could automatically add the uncertified version when loading a certified SSH key
  • term-reset-title: Perhaps terminal resets should reset window title(s)
  • triple-click-wrap: Perhaps triple-click select should take account of wrapped lines
  • two-way-keepalives: An alternative form of keepalive which is two-way
  • vt-utf8-keyboard: Keyboard mode to support Microsoft standard serial consoles
  • xterm-keyboard: Better xterm keyboard compatibility
• "tricky": Needs many tuits.
  • colour-scheme: Predefined colour schemes
  • cooked-printer: Feature-rich printer support with formatting control
  • dll-frontend: SSH client packaged as a DLL for use in other programs
  • drag-drop: Drag and drop support
  • gui-auth: Option to use GUI dialogs for authentication
  • gui-sftp: A GUI client for SFTP
  • horiz-scroll: Horizontal scrollbar
  • http-proxy-server: Present HTTP proxy interface to dynamic port forwarding
  • idn: Support for Internationalized Domain Names (IDNs)
  • ip-tos: Use of IP type-of-service field
  • key-formats-natively: Ability to use OpenSSH and ssh.com SSH-2 private keys directly (without first converting with PuTTYgen)
  • keyboard-copy: Should be able to copy to clipboard without mouse
  • log-timestamp: Timestamps in logs
  • mdpi: The mythical DLL Plugin Interface
  • multiple-connections: Managing multiple connections in one PuTTY (eg. tabbed windows, MDI)
  • pageant-unix-either-or: Agnostic agent/client mode in Unix Pageant
  • pageant-wayland: Unix Pageant should support GUI session lifetime on Wayland
  • paste-fidelity: Extra fidelity in copy and paste operations
  • plink-background: Plink option to background after authentication
  • portfwd-dynamic-remote: Remote-to-local SOCKS-based dynamic port forwarding
  • print-screen: "Print screen" and similar functions
  • pscp-multi-remote-src: Perhaps PSCP should permit multiple remote sources
  • pscp-restart: Restart capability in PSCP
  • psftp-remget: Restart multiple-file operations in PSFTP
  • putty-screen-frontend: screen(1) front-end
  • puttygen-batch: Batch mode for Windows PuTTYgen
  • regexp-logging: Selective logging based on regular expressions
  • rsh-backend: rsh and rexec backends
  • scripting: Scripting support in PuTTY
  • scrollbar-left: Scroll bar on the left of the PuTTY window
  • session-icon: Custom, per-session configurable icons
  • sshfp-dns: Support for host key fingerprints in DNS
  • subsystem-publickey: Support for public key distribution subsystem `publickey'
  • toolbar: Toolbar on the PuTTY window
  • typographical-metrics: Make PuTTY use the typographical metrics in TrueType fonts
  • unicode-normalisation: Apply Unicode normalisation to combining characters
  • unix-persistent-bell: Persistent bell indication on Unix
  • url-launching: Launch URLs displayed in the PuTTY window by clicking on them
  • zmodem: File transfers using Zmodem
• "taxing": Needs external things we don't have (standards, users etc)
  • fido2: Support for U2F / FIDO2 security keys via 'sk-foo@openssh.com' public-key types
  • function-keys: Function and other special keys don't do what people want
  • modified-fkeys: Unique codes for modified function/special keys
  • mosh: Compatibility with Mosh (mobile shell)
  • pageant-forwarding-path: Track and use the agent-forwarding path in Pageant
  • sco-ansi: Support for `SCO ANSI' terminal features
  • smartcard-auth: PuTTY could use RSA keys held on smartcards
• "mayhem": Probably impossible
  • drag-drop-to-cwd: Drag and drop support (the hard version)
  • moon-on-stick: The Moon, on a stick

Non-wish list

These are features we are actively opposed to seeing in PuTTY. Don't bother writing them and sending them to us! If you think you have a good argument why they would be good, feel free to plead for them, but generally I'll already have a good reason not to do them.

• accept-host-keys: An option to accept all SSH host keys
• banner-escape-codes: Interpret escape codes in pre-login banner
• compress-binaries: Compress shipped PuTTY binaries with a tool such as UPX
• control-window-pos: Remember window position, or allow it to be configured
• inhibit-close: Ability to remove close box from window
• locking-settings: Ability to lock settings against user changes
• mud-client: MUD-client-like features (separate input window, etc)
• osc: Escape sequence to execute command on the client side
• osc8: Support for the OSC 8 control sequence to associate cells of the terminal with an unrelated URL
• pageant-as-service: Ability to run Pageant as a Windows Service in NT/2000/etc
• plink-terminal: Terminal emulation in Plink
• port-knocking: Port knocking
• reconnect-remember-password: Remember entered password for reconnecting a dead session
• remember-password: Ability to store password in settings
• sftp-as-drive: Present SFTP as a mapped drive or file system
• system-tray: Use of the System tray
• terminal-emulations: Terminal emulations other than xterm/ECMA-48 (e.g. 3270)
• terminal-fanout: Send keyboard input to multiple active sessions
• transparency: Transparent or translucent PuTTY window
• tun-openssh: OpenSSH-compatible tun VPN support

Unclassified

Usually items we don't know enough about, or haven't yet thought about enough, to fully classify.

• cipher-selection: Cipher selection UI is messy and irrational
• foundry-ignore-bug: Foundry Networks 1.2.27 port has SSH_MSG_IGNORE bug
• fullscreen-menu-corner: Use other corners for menu in full-screen mode
• host-key-rollover: Host key/algorithm rollover not well supported
• psftp-batch-interact: PSFTP: continue interactively after a batch script
• ssh2-romsshell-badstringlen: Embedded RomSShell server closes connection with "Bad string Length"
• virtuallock: Use of VirtualLock() on Windows for sensitive material

Historic issues

Here's a link to a subpage of historic issues, which probably aren't interesting any more unless you're doing archaeology.