Out-of-bounds write in the kitty text sizing protocol allows termination of the terminal process
Summary
| CVE | CVE-2026-80431 |
|---|---|
| State | PUBLISHED |
| Assigner | Secur0 |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-25 14:17:19 UTC |
| Updated | 2026-09-25 16:17:27 UTC |
| 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. |
Risk And Classification
Primary CVSS: v4.0 6.8 MEDIUM from 4daa8cea-433a-44bd-9456-53b127fc289a
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: 0.001360000 probability, percentile 0.025110000 (date 2026-09-27)
Problem Types: CWE-787 | CWE-787 CWE-787 Out-of-bounds Write
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | 4daa8cea-433a-44bd-9456-53b127fc289a | Secondary | 6.8 | MEDIUM | 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/C... |
| 4.0 | CNA | CVSS | 6.8 | MEDIUM | 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 |
CVSS v4.0 Breakdown
Attack Vector
LocalAttack Complexity
LowAttack Requirements
NonePrivileges Required
NoneUser Interaction
PassiveConfidentiality
NoneIntegrity
NoneAvailability
HighSub Conf.
NoneSub Integrity
NoneSub Availability
NoneCVSS: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
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Kovid Goyal | Kitty | affected 0.40.0 0.49.0 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| secur0.com/en/cna/cve-list/cve-2026-80431-kitty-text-sizing-out-of-bound... | 4daa8cea-433a-44bd-9456-53b127fc289a | secur0.com | |
| github.com/kovidgoyal/kitty/commit/7d2fbaadcc2b1eeeef89bd875ec622b42362574b | 4daa8cea-433a-44bd-9456-53b127fc289a | github.com | |
| github.com/kovidgoyal/kitty/releases/tag/v0.49.0 | 4daa8cea-433a-44bd-9456-53b127fc289a | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: C4sh3R (en)
CNA: Cristian Fernández Cornejo (en)
CNA: Xoán M. Otero Jorge (en)
CNA: Secur0 CNA (en)
CNA: Kovid Goyal (en)
Additional Advisory Data
Solutions
CNA: Upgrade to kitty 0.49.0 or later.
There are currently no legacy QID mappings associated with this CVE.