CVE-2026-80431

MEDIUMPre-NVD 6.86.8—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.1% (2nd percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 3 sources updated this week
6.8EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.1%CVSS: 6.8Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
6.8
EG Score
6.8MEDIUMmedium confidence
EG Risk
35
EG Risk 35/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity68% × 45%
Exploitation0% × 40%
Automatability30% × 15%
CISA SSVC: Track at low or medium mission impact; Track or Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.1%
EPSS %ILE
2nd
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track or Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation none (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 25, 2026

Last Modified

September 29, 2026

Advisory Details (3)

Auto-updated Sep 25, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_release.
generic🟡 PoC Available

CVE-2026-80431 · Out-of-bounds write in the kitty text sizing protocol allows termination of the terminal process | Vulnerabilities published by Secur0

https://secur0.com/en/cna/cve-list/cve-2026-80431-kitty-text-sizing-out-of-bounds-write
github_release Patch Available

version 0.49.0

Patch available: kovidgoyal/kitty v0.49.0

https://github.com/kovidgoyal/kitty/releases/tag/v0.49.0
github_commit

commit 7d2fbaadcc2b (kovidgoyal/kitty)

Fix landed in kovidgoyal/kitty commit 7d2fbaadcc2b — awaiting tagged release

https://github.com/kovidgoyal/kitty/commit/7d2fbaadcc2b1eeeef89bd875ec622b42362574b

Vendor Advisories for CVE-2026-80431(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 21× in last 7d / 27× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-03 15:59 UTCEG score recompute
  2. 2026-10-03 15:59 UTCGHSA enrichment
  3. 2026-10-03 14:26 UTCEPSS rescore
  4. 2026-10-02 17:57 UTCEPSS rescore
  5. 2026-10-02 17:33 UTCEG score recompute
  6. 2026-10-02 17:33 UTCGHSA enrichment
  7. 2026-10-01 19:50 UTCEPSS rescore
  8. 2026-10-01 19:07 UTCGHSA enrichment
  9. 2026-09-30 20:42 UTCEG score recompute
  10. 2026-09-30 20:42 UTCGHSA enrichment
  11. 2026-09-30 15:04 UTCEPSS rescore
  12. 2026-09-29 22:18 UTCEG score recompute
  13. 2026-09-29 22:17 UTCGHSA enrichment
  14. 2026-09-29 10:15 UTCEG score recompute
  15. 2026-09-29 10:15 UTCGHSA enrichment
  16. 2026-09-28 13:52 UTCEPSS rescore
  17. 2026-09-28 11:44 UTCEG score recompute
  18. 2026-09-28 11:44 UTCGHSA enrichment
  19. 2026-09-27 13:48 UTCEPSS rescore
  20. 2026-09-27 13:19 UTCEG score recompute
  21. 2026-09-27 13:19 UTCGHSA enrichment
  22. 2026-09-26 15:59 UTCEPSS rescore
  23. 2026-09-26 14:54 UTCGHSA enrichment
  24. 2026-09-25 16:27 UTCGHSA enrichment
  25. 2026-09-25 14:22 UTCEG score recompute
Show 2 more
  1. 2026-09-25 13:36 UTCEG score recompute
  2. 2026-09-25 13:34 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-80431?
CVE-2026-80431 is a medium vulnerability published on September 25, 2026. 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 screenhandlemulticellcommand() in kitty/screen.c appends each codepoint of a grapheme cluster…
When was CVE-2026-80431 disclosed?
CVE-2026-80431 was first published on September 25, 2026, with the most recent update on September 29, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-80431 actively exploited?
CVE-2026-80431 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.1% probability of exploitation in the next 30 days (2nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-80431?
CVE-2026-80431 has a CVSS base score of 6.8 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-80431?
A fix for CVE-2026-80431 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-80431 are linked in the Vendor Advisories panel on this page.

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