CVE-2026-80431
Out-of-bounds write in the kitty text sizing protocol allows termination of the terminal process
- Published
- Updated
- Reserved
- Assigned by
- Secur0
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| Secur0CNA (assigner) | 4.0 | Medium6.8 | 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 |
| NVDNVD · Awaiting Analysis | 4.0 | Medium6.8 | 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 |
- EPSS (exploitation in 30 days)
- 0.13% · top 97% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.8.
Weakness
Affected products
- affected 0.40.0 – < 0.49.0
What to do
Solution: Upgrade to kitty 0.49.0 or later.
References (3)
- https://github.com/kovidgoyal/kitty/commit/7d2fbaadcc2b1eeeef89bd875ec622b42362574b (opens in a new tab)patch
- https://github.com/kovidgoyal/kitty/releases/tag/v0.49.0 (opens in a new tab)release-notes
- https://secur0.com/en/cna/cve-list/cve-2026-80431-kitty-text-sizing-out-of-bounds-write (opens in a new tab)third-party-advisorytechnical-description
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-80431)Record last updated .