{"id":"CVE-2026-80431","aliases":["DEBIAN-CVE-2026-80431","EUVD-2026-87088","GHSA-fx7r-q727-j825","UBUNTU-CVE-2026-80431"],"status":"published","title":"Out-of-bounds write in the kitty text sizing protocol allows termination of the terminal process","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.","severity":{"version":"4.0","score":6.8,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00134,"percentile":0.02955,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-787"],"published":"2026-09-25T13:23:51Z","modified":"2026-10-28T11:01:30Z","affected":[{"source":"osv","ecosystem":"Debian:12","package":"kitty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.26.5-5","0.30.1-1","0.31.0-1","0.31.0-2","0.31.0-3","0.31.0-4","0.32.0-1","0.32.1-1","0.32.2-1","0.33.0-2","0.33.1-1","0.34.1-1","0.35.1-1","0.35.2-1","0.36.1-1","0.36.4-1","0.36.4-2","0.36.4-3","0.37.0-1","0.38.1-1","0.39.0-1","0.39.1-1","0.40.0-1","0.41.1-1","0.41.1-2","0.42.1-1","0.42.2-1","0.43.1-1","0.44.0-1","0.45.0-1","0.45.0-2","0.46.1-1","0.46.2-1","0.47.0-1","0.47.0-2","0.47.0-3","0.47.3-1","0.47.4-1","0.48.2-1","0.48.2-1.1"]},{"source":"osv","ecosystem":"Debian:13","package":"kitty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.41.1-2","0.41.1-2+deb13u1","0.41.1-2+deb13u2","0.42.1-1","0.42.2-1","0.43.1-1","0.44.0-1","0.45.0-1","0.45.0-2","0.46.1-1","0.46.2-1","0.47.0-1","0.47.0-2","0.47.0-3","0.47.3-1","0.47.4-1","0.48.2-1","0.48.2-1.1"]},{"source":"osv","ecosystem":"Debian:14","package":"kitty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.41.1-2","0.42.1-1","0.42.2-1","0.43.1-1","0.44.0-1","0.45.0-1","0.45.0-2","0.46.1-1","0.46.2-1","0.47.0-1","0.47.0-2","0.47.0-3","0.47.3-1","0.47.4-1","0.48.2-1","0.48.2-1.1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:20.04:LTS","package":"kitty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.14.3-1","0.14.4-1","0.14.6-1","0.15.0-1","0.15.0-1build1","0.15.0-1ubuntu0.2","0.15.0-1ubuntu0.2+esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:22.04:LTS","package":"kitty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.19.3-1","0.21.2-1","0.21.2-1build1","0.21.2-1ubuntu0.22.04.1","0.21.2-1ubuntu0.22.04.1+esm1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:24.04:LTS","package":"kitty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.26.5-3ubuntu2","0.26.5-5ubuntu1","0.31.0-3","0.31.0-4","0.32.2-1","0.32.2-1build2","0.32.2-1build3","0.32.2-1ubuntu0.1","0.32.2-1ubuntu0.2","0.32.2-1ubuntu0.3","0.32.2-1ubuntu0.4","0.32.2-1ubuntu0.4+esm1","0.32.2-1ubuntu0.4+esm2"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"kitty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.45.0-1build1","0.47.0-3","0.47.4-1","0.48.2-1.1ubuntu1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:26.04:LTS","package":"kitty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.41.1-2","0.43.1-1","0.44.0-1","0.45.0-1","0.45.0-1build1","0.45.0-1ubuntu0.1~esm1","0.45.0-1ubuntu0.1~esm2"]}],"products":[{"vendor":"kitty project","product":"kitty"},{"vendor":"kovid goyal","product":"kitty"}],"references":[{"url":"https://github.com/kovidgoyal/kitty/commit/7d2fbaadcc2b1eeeef89bd875ec622b42362574b","tags":["patch","fix","report"]},{"url":"https://github.com/kovidgoyal/kitty/releases/tag/v0.49.0","tags":["release-notes","advisory","report"]},{"url":"https://secur0.com/en/cna/cve-list/cve-2026-80431-kitty-text-sizing-out-of-bounds-write","tags":["third-party-advisory","technical-description","advisory","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-80431","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-fx7r-q727-j825"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80431.json","tags":["advisory"]},{"url":"https://github.com/kovidgoyal/kitty","tags":["package"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-80431","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-80431","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-80431","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-80431","title":"Out-of-bounds write in the kitty text sizing protocol allows termination of the terminal process","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.","status":"published","published":"2026-09-25T13:23:51.59Z","modified":"2026-09-25T15:07:45.536Z","cvss":[{"version":"4.0","score":6.8,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"medium","assessor":"cna"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T13:45:36.695039Z"}],"euvd":[{"id":"EUVD-2026-87088","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.","status":"published","published":"2026-09-25T13:23:51Z","modified":"2026-09-25T15:07:45Z","cvss":[{"version":"4.0","score":6.8,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-02T17:27:55.413842Z"}],"ghsa":[{"id":"GHSA-fx7r-q727-j825","title":"Out-of-bounds Write in the natural width branch of the text sizing protocol in kitty from 0.40.0...","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.","status":"published","published":"2026-09-25T15:31:47Z","modified":"2026-09-25T15:31:54Z","cvss":[{"version":"4.0","score":6.8,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T15:12:27.190195Z"}],"nvd":[{"id":"CVE-2026-80431","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.","status":"published","published":"2026-09-25T14:17:19.253Z","modified":"2026-09-29T21:32:59.833Z","cvss":[{"version":"4.0","score":6.8,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium","assessor":"secondary"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T14:12:51.721923Z"}],"osv":[{"id":"CVE-2026-80431","title":"Out-of-bounds write in the kitty text sizing protocol allows termination of the terminal process","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.","status":"published","published":"2026-09-25T13:23:51.59Z","modified":"2026-10-28T11:01:30.606009411Z","cvss":[{"version":"4.0","score":6.8,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-787"],"updated_at":"2026-11-02T15:45:17.44708Z"},{"id":"DEBIAN-CVE-2026-80431","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.","status":"published","published":"2026-09-25T14:17:19.253Z","modified":"2026-09-30T08:47:33.741715938Z","cvss":[{"version":"4.0","score":6.8,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium"}],"updated_at":"2026-11-02T15:46:04.001673Z"},{"id":"UBUNTU-CVE-2026-80431","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.","status":"published","published":"2026-09-25T14:17:00Z","modified":"2026-10-17T13:01:10.480065892Z","cvss":[{"version":"4.0","score":6.8,"vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-02T16:57:18.015985Z"}]}}