CVE-2026-79591

HIGHPre-NVD 7.87.8—
EchelonGraph scoreHIGH confidence

Score 7.8 from GitHub Security Advisory (severity: HIGH) published 2026-09-10. CISA-ADP (Vulnrichment) CVSS v3.1 baseline 7.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: cisa-adp, epss, ghsa
Trending — 4 sources updated this weekElevated
7.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.8Exploit: Elevated riskExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

A heap-buffer-overflow and use-after-free vulnerability exists in the xls_getCSS() function of libxls 1.6.3 due to insufficient validation of a file-controlled font index.

CVSS v3
7.8
EG Score
7.8(high)
EG Risk
51(Track*)
EG Risk 51/100SSVC: Track*

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
Severity78% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
0%
EPSS %ILE
3%
KEV
Not listed

Published

September 10, 2026

Last Modified

September 15, 2026

Advisory Details (2)

Auto-updated Sep 15, 2026
Upstream fix merged — awaiting tagged release. Sources: github_pr.
github_pr

Validate font indices when generating CSS

Fix merged in libxls/libxls PR #164 on 2026-08-21 — awaiting tagged release

https://github.com/libxls/libxls/pull/164/changes/902c8f9b13710c3a13b6232fb86626c5c729402c
generic

[Bug]heap-buffer-overflow / use-after-free in xls_getCSS() from an unchecked file-controlled font index (CWE-125) · Issue #161 · libxls/libxls · GitHub

https://github.com/libxls/libxls/issues/161

Vendor Advisories for CVE-2026-79591(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 29× in last 7d / 36× 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. 2026-09-21 05:04 UTCEG score recompute
  2. 2026-09-21 05:04 UTCGHSA enrichment
  3. 2026-09-20 20:16 UTCEPSS rescore
  4. 2026-09-20 18:05 UTCGHSA enrichment
  5. 2026-09-20 07:02 UTCGHSA enrichment
  6. 2026-09-19 19:50 UTCEG score recompute
  7. 2026-09-19 19:50 UTCGHSA enrichment
  8. 2026-09-19 08:51 UTCGHSA enrichment
  9. 2026-09-18 21:51 UTCEG score recompute
  10. 2026-09-18 21:51 UTCGHSA enrichment
  11. 2026-09-18 19:28 UTCEPSS rescore
  12. 2026-09-18 10:53 UTCGHSA enrichment
  13. 2026-09-17 23:54 UTCEG score recompute
  14. 2026-09-17 23:54 UTCGHSA enrichment
  15. 2026-09-17 11:49 UTCGHSA enrichment
  16. 2026-09-17 00:51 UTCEG score recompute
  17. 2026-09-17 00:51 UTCGHSA enrichment
  18. 2026-09-16 14:08 UTCEPSS rescore
  19. 2026-09-16 13:53 UTCEG score recompute
  20. 2026-09-16 13:53 UTCGHSA enrichment
  21. 2026-09-16 05:15 UTCEPSS rescore
  22. 2026-09-16 02:32 UTCGHSA enrichment
  23. 2026-09-15 15:34 UTCEG score recompute
  24. 2026-09-15 15:34 UTCGHSA enrichment
  25. 2026-09-15 14:18 UTCEG score recompute▲ 7.80
Show 11 more
  1. 2026-09-15 14:18 UTCGHSA enrichment
  2. 2026-09-15 14:18 UTCMITRE cvelistV5CVSS v3 → 7.8 · severity → HIGH
  3. 2026-09-15 03:12 UTCEPSS rescore
  4. 2026-09-15 03:12 UTCEPSS rescore
  5. 2026-09-13 19:44 UTCEG score recompute
  6. 2026-09-13 19:44 UTCGHSA enrichment
  7. 2026-09-11 14:53 UTCEPSS rescore
  8. 2026-09-11 14:53 UTCEPSS rescore
  9. 2026-09-10 21:18 UTCNVD update
  10. 2026-09-10 20:45 UTCEG score recompute
  11. 2026-09-10 20:44 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-79591?
CVE-2026-79591 is a high vulnerability published on September 10, 2026. A heap-buffer-overflow and use-after-free vulnerability exists in the xls_getCSS() function of libxls 1.6.3 due to insufficient validation of a file-controlled font index.
When was CVE-2026-79591 disclosed?
CVE-2026-79591 was first published in the National Vulnerability Database on September 10, 2026, with the most recent update on September 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-79591 actively exploited?
CVE-2026-79591 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 97.3% of all scored CVEs.
What is the CVSS score of CVE-2026-79591?
CVE-2026-79591 has a CVSS v3.1 base score of 7.8 (CISA-ADP / Vulnrichment enrichment; NVD's own analysis pending).
How do I remediate CVE-2026-79591?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-79591, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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