{"id":"CVE-2026-80431","published":"2026-09-25T14:17:19.253","lastModified":"2026-09-29T21:32:59.833","description":"Out-of-bounds Write in the natural width branch of the text sizing protocol in kitty from 0.40.0 before 0.49.0 allows a program writing to the terminal to write past the end of a fixed-size buffer, because screen_handle_multicell_command() in kitty/screen.c appends each codepoint of a grapheme cluster with lc.chars[lc.count++] = ch without any capacity check, while lc is declared by the RAII_ListOfChars macro as a four-element char_type array in the function's stack frame, so an OSC 66 escape code whose payload carries a grapheme cluster longer than four codepoints writes beyond that buffer, one 32-bit value per additional codepoint, in the order the codepoints appear. Where the cluster is preceded in the same payload by a sequence that causes an intermediate flush, the buffer is first migrated to the heap by ensure_space_for_chars() and the write occurs past the heap allocation instead. This results in termination of the kitty process and therefore of all its windows, tabs and child processes.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":["CWE-787"],"vendors":[],"products":[],"references":[{"url":"https://github.com/kovidgoyal/kitty/commit/7d2fbaadcc2b1eeeef89bd875ec622b42362574b","tags":[]},{"url":"https://github.com/kovidgoyal/kitty/releases/tag/v0.49.0","tags":[]},{"url":"https://secur0.com/en/cna/cve-list/cve-2026-80431-kitty-text-sizing-out-of-bounds-write","tags":[]}],"exploitRefs":[{"url":"https://github.com/kovidgoyal/kitty/commit/7d2fbaadcc2b1eeeef89bd875ec622b42362574b","tags":[]},{"url":"https://github.com/kovidgoyal/kitty/releases/tag/v0.49.0","tags":[]}],"hasPoc":true,"ai":null}