CVE-2026-85091

HIGHPre-NVD 7.47.4—
EchelonGraph scoreHIGH confidence

Score 7.4 from GitHub Security Advisory (severity: HIGH) published 2026-09-03. a secondary CVSS source baseline 7.4; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 4 sources updated this weekElevated
7.4EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.4Exploit: Elevated riskExposed: 0

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

zlib versions 1.3.1.2 through 1.3.2 contain a heap buffer overflow vulnerability in the gz_vacate() function when processing non-blocking gzwrite() operations with stale external buffer pointers. Attackers can trigger the overflow by calling gzprintf() or gzvprintf() after a write stall, causing an unchecked memmove() to write beyond the internal input buffer boundary.

CVSS v3
7.4
EG Score
7.4(high)
EG Risk
49(Track*)
EG Risk 49/100SSVC: 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
Severity74% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
0%
EPSS %ILE
38%
KEV
Not listed

Published

September 3, 2026

Last Modified

September 9, 2026

Advisory Details (4)

Auto-updated Sep 3, 2026
🔬 Proof of concept available. No patch confirmed yet.
generic🟡 PoC Available

zlib 1.3.1.2 through 1.3.2 Heap Buffer Overflow via gz_vacate | Advisories | VulnCheck

https://www.vulncheck.com/advisories/zlib-1.3.1.2-through-1.3.2-heap-buffer-overflow-via-gz-vacate
generic

GitHub - madler/zlib: A massively spiffy yet delicately unobtrusive compression library. · GitHub

https://github.com/madler/zlib
generic

zlib/gzwrite.c at v1.3.2 · madler/zlib · GitHub

https://github.com/madler/zlib/blob/v1.3.2/gzwrite.c#L393
generic🟡 PoC Available

zlib gz_vacate() Heap-Buffer Overflow via Non-Blocking Write · GitHub

https://gist.github.com/thesmartshadow/e0b9481792afb7c31e86fee1ff084490

Vendor Advisories for CVE-2026-85091(2)

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

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFixed inDependents
zlib1:1.2.13.dfsg-1 ... 1:1.3.dfsg-3.1~exp1 (14 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
zlib1:1.3.dfsg+really1.3.1-1 ... 1:1.3.dfsg+really1.3.2-3 (6 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
zlib1:1.3.dfsg+really1.3.1-1 ... 1:1.3.dfsg+really1.3.2-3 (6 versions)——

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 41× in last 7d / 88× 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. 2026-09-19 14:15 UTCVendor advisory
  2. 2026-09-19 14:15 UTCGHSA enrichment
  3. 2026-09-19 01:58 UTCEG score recompute
  4. 2026-09-19 01:58 UTCVendor advisory
  5. 2026-09-19 01:58 UTCGHSA enrichment
  6. 2026-09-18 19:28 UTCEPSS rescore
  7. 2026-09-18 13:42 UTCVendor advisory
  8. 2026-09-18 13:42 UTCGHSA enrichment
  9. 2026-09-18 01:25 UTCEG score recompute
  10. 2026-09-18 01:25 UTCVendor advisory
  11. 2026-09-18 01:25 UTCGHSA enrichment
  12. 2026-09-17 19:32 UTCEPSS rescore
  13. 2026-09-17 13:08 UTCVendor advisory
  14. 2026-09-17 13:08 UTCGHSA enrichment
  15. 2026-09-17 00:51 UTCEG score recompute
  16. 2026-09-17 00:51 UTCVendor advisory
  17. 2026-09-17 00:51 UTCGHSA enrichment
  18. 2026-09-16 14:09 UTCEPSS rescore
  19. 2026-09-16 12:34 UTCEG score recompute
  20. 2026-09-16 12:34 UTCVendor advisory
  21. 2026-09-16 12:34 UTCGHSA enrichment
  22. 2026-09-16 05:15 UTCEPSS rescore
  23. 2026-09-16 00:17 UTCVendor advisory
  24. 2026-09-16 00:17 UTCGHSA enrichment
  25. 2026-09-15 11:59 UTCEG score recompute
Show 63 more
  1. 2026-09-15 11:59 UTCVendor advisory
  2. 2026-09-15 11:59 UTCGHSA enrichment
  3. 2026-09-15 03:12 UTCEPSS rescore
  4. 2026-09-15 03:12 UTCEPSS rescore
  5. 2026-09-14 23:42 UTCVendor advisory
  6. 2026-09-14 23:42 UTCGHSA enrichment
  7. 2026-09-14 11:25 UTCVendor advisory
  8. 2026-09-14 11:25 UTCGHSA enrichment
  9. 2026-09-13 23:08 UTCEG score recompute
  10. 2026-09-13 23:08 UTCVendor advisory
  11. 2026-09-13 23:08 UTCGHSA enrichment
  12. 2026-09-13 10:51 UTCVendor advisory
  13. 2026-09-13 10:51 UTCGHSA enrichment
  14. 2026-09-12 22:34 UTCEG score recompute
  15. 2026-09-12 22:34 UTCVendor advisory
  16. 2026-09-12 22:34 UTCGHSA enrichment
  17. 2026-09-12 10:17 UTCVendor advisory
  18. 2026-09-12 10:17 UTCGHSA enrichment
  19. 2026-09-11 22:00 UTCEG score recompute
  20. 2026-09-11 22:00 UTCVendor advisory
  21. 2026-09-11 22:00 UTCGHSA enrichment
  22. 2026-09-11 14:53 UTCEPSS rescore
  23. 2026-09-11 14:53 UTCEPSS rescore
  24. 2026-09-11 09:43 UTCEG score recompute
  25. 2026-09-11 09:43 UTCVendor advisory
  26. 2026-09-11 09:43 UTCGHSA enrichment
  27. 2026-09-10 21:26 UTCEG score recompute
  28. 2026-09-10 21:26 UTCGHSA enrichment
  29. 2026-09-10 09:09 UTCGHSA enrichment
  30. 2026-09-09 20:50 UTCVendor advisory
  31. 2026-09-09 20:50 UTCGHSA enrichment
  32. 2026-09-09 11:27 UTCVendor advisory
  33. 2026-09-09 11:27 UTCGHSA enrichment
  34. 2026-09-08 23:10 UTCEG score recompute
  35. 2026-09-08 23:10 UTCVendor advisory
  36. 2026-09-08 23:10 UTCGHSA enrichment
  37. 2026-09-08 22:01 UTCEPSS rescore
  38. 2026-09-08 05:09 UTCVendor advisory
  39. 2026-09-08 05:09 UTCGHSA enrichment
  40. 2026-09-07 16:50 UTCEG score recompute
  41. 2026-09-07 16:50 UTCVendor advisory
  42. 2026-09-07 16:50 UTCGHSA enrichment
  43. 2026-09-07 04:34 UTCVendor advisory
  44. 2026-09-07 04:34 UTCGHSA enrichment
  45. 2026-09-06 16:17 UTCEG score recompute
  46. 2026-09-06 16:17 UTCVendor advisory
  47. 2026-09-06 16:17 UTCGHSA enrichment
  48. 2026-09-06 13:48 UTCEPSS rescore
  49. 2026-09-06 04:00 UTCGHSA enrichment
  50. 2026-09-05 15:43 UTCEG score recompute
  51. 2026-09-05 15:43 UTCGHSA enrichment
  52. 2026-09-05 15:31 UTCEPSS rescore
  53. 2026-09-05 03:25 UTCGHSA enrichment
  54. 2026-09-04 15:08 UTCEG score recompute
  55. 2026-09-04 15:08 UTCGHSA enrichment
  56. 2026-09-04 05:07 UTCEPSS rescore
  57. 2026-09-04 02:51 UTCEG score recompute
  58. 2026-09-04 02:50 UTCGHSA enrichment
  59. 2026-09-03 14:30 UTCEG score recompute
  60. 2026-09-03 13:25 UTCEG score recompute
  61. 2026-09-03 13:15 UTCEG score recompute
  62. 2026-09-03 01:09 UTCEG score recompute
  63. 2026-09-03 01:09 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-85091?
CVE-2026-85091 is a high vulnerability published on September 3, 2026. zlib versions 1.3.1.2 through 1.3.2 contain a heap buffer overflow vulnerability in the gz_vacate() function when processing non-blocking gzwrite() operations with stale external buffer pointers. Attackers can trigger the overflow by calling gzprintf() or gzvprintf() after a write stall, causing an…
When was CVE-2026-85091 disclosed?
CVE-2026-85091 was first published in the National Vulnerability Database on September 3, 2026, with the most recent update on September 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-85091 actively exploited?
CVE-2026-85091 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 62.2% of all scored CVEs.
What is the CVSS score of CVE-2026-85091?
CVE-2026-85091 has a CVSS v3 base score of 7.4 (NVD).
How do I remediate CVE-2026-85091?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-85091, 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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