PuTTY on Windows crashes whenever I copy more than roughly 100 lines containing UTF-8 characters, especially box-drawing symbols such as ├─ and bullets. The problem occurs with automatic selection copying, Ctrl+Ins, and the right-click Copy action.
I reproduced it by connecting to Linux and running `fwupdmgr get-devices`, then selecting the output. It happens with PuTTY 0.76, 0.78, and 0.85, in both 32-bit and 64-bit builds, on Windows 10. I tried different fonts, scrollback settings, clipboard options, administrator mode, and restricted ACL mode, but explicit copying still crashed. There are no third-party clipboard managers installed. Windows Event Viewer reports an access violation in ntdll.dll.
Has anyone else encountered this, or found a reliable workaround?
4 Answers
Switching to another SSH client is an option, but PuTTY’s small footprint, saved session settings, Pageant integration, and companion tools such as PSCP and PSFTP can make replacing the whole setup inconvenient. Fixing the RTF clipboard option is less disruptive if the rest of the ecosystem is working well.
Increasing scrollback probably won’t help if the crash happens during clipboard conversion. The issue can occur even with a very large scrollback buffer, so the relevant setting is the clipboard format rather than the amount of terminal history.
The culprit turned out to be PuTTY’s “Copy in clipboard RTF” option. Disabling that setting stopped the crash completely. It seems to be related to how PuTTY converts UTF-8 terminal text into Windows rich-text clipboard data, particularly when the selection contains box-drawing characters or other unusual whitespace.
A practical fallback is to log the session to a text file and copy from that, although it’s understandably less convenient than selecting text directly in the terminal.
Logging does preserve the output, but I specifically needed to copy only the text I want on demand. Disabling clipboard RTF fixed the direct-copy workflow.