{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-80431","assignerOrgId":"4daa8cea-433a-44bd-9456-53b127fc289a","state":"PUBLISHED","assignerShortName":"Secur0","dateReserved":"2026-08-26T10:49:01.410Z","datePublished":"2026-09-25T13:23:51.590Z","dateUpdated":"2026-09-25T15:07:45.536Z"},"containers":{"cna":{"providerMetadata":{"orgId":"4daa8cea-433a-44bd-9456-53b127fc289a","shortName":"Secur0","dateUpdated":"2026-09-25T13:23:51.590Z"},"title":"Out-of-bounds write in the kitty text sizing protocol allows termination of the terminal process","datePublic":"2026-09-21T04:01:00.000Z","problemTypes":[{"descriptions":[{"lang":"en","cweId":"CWE-787","description":"CWE-787 Out-of-bounds Write","type":"CWE"}]}],"impacts":[{"capecId":"CAPEC-100","descriptions":[{"lang":"en","value":"CAPEC-100 Overflow Buffers"}]}],"affected":[{"vendor":"Kovid Goyal","product":"kitty","repo":"https://github.com/kovidgoyal/kitty","programFiles":["kitty/screen.c"],"versions":[{"status":"affected","version":"0.40.0","lessThan":"0.49.0","versionType":"semver"}],"defaultStatus":"unaffected"}],"cpeApplicability":[{"operator":"OR","nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:kovidgoyal:kitty:*:*:*:*:*:*:*:*","versionStartIncluding":"0.40.0","versionEndExcluding":"0.49.0"}]}]}],"descriptions":[{"lang":"en","value":"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.","supportingMedia":[{"type":"text/html","base64":false,"value":"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 <code>screen_handle_multicell_command()</code> in <code>kitty/screen.c</code> appends each codepoint of a grapheme cluster with <code>lc.chars[lc.count++] = ch</code> without any capacity check, while <code>lc</code> is declared by the <code>RAII_ListOfChars</code> macro as a four-element <code>char_type</code> 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 <code>ensure_space_for_chars()</code> 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."}]}],"tags":["x_open-source"],"references":[{"url":"https://github.com/kovidgoyal/kitty/commit/7d2fbaadcc2b1eeeef89bd875ec622b42362574b","tags":["patch"]},{"url":"https://github.com/kovidgoyal/kitty/releases/tag/v0.49.0","tags":["release-notes"]},{"url":"https://secur0.com/en/cna/cve-list/cve-2026-80431-kitty-text-sizing-out-of-bounds-write","tags":["third-party-advisory","technical-description"]}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV4_0":{"attackVector":"LOCAL","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"PASSIVE","vulnConfidentialityImpact":"NONE","subConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","subIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED","version":"4.0","baseSeverity":"MEDIUM","baseScore":6.8,"vectorString":"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"}}],"solutions":[{"lang":"en","value":"Upgrade to kitty 0.49.0 or later.","supportingMedia":[{"type":"text/html","base64":false,"value":"Upgrade to kitty 0.49.0 or later."}]}],"credits":[{"lang":"en","value":"C4sh3R","type":"finder"},{"lang":"en","value":"Cristian Fernández Cornejo","type":"analyst"},{"lang":"en","value":"Xoán M. Otero Jorge","type":"analyst"},{"lang":"en","value":"Secur0 CNA","type":"coordinator"},{"lang":"en","value":"Kovid Goyal","type":"remediation developer"}],"source":{"discovery":"EXTERNAL"},"x_generator":{"engine":"Vulnogram 1.0.5"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-25T15:05:06.462333Z","id":"CVE-2026-80431","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-09-25T15:07:45.536Z"}}]}}