CVE-2026-86250

HIGHPre-NVD 7.57.5—
EchelonGraph scoreHIGH confidence

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-09-06. a secondary CVSS source baseline 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this week
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.5Exploit: None knownExposed: 0

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

h3 versions before 2.0.1-rc.18 fail to validate the chunk count parsed from user-controlled cookie values in setChunkedCookie() and deleteChunkedCookie() functions. Attackers can send a crafted cookie header with an extremely large chunk count to trigger an O(n²) cleanup loop that hangs the server process.

CVSS v3
7.5
EG Score
7.5(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
Severity75% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
21%
KEV
Not listed

Published

September 6, 2026

Last Modified

September 18, 2026

Advisory Details (2)

Auto-updated Sep 6, 2026
🔬 Proof of concept available. Patch available. Sources: github.
generic

h3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked Cookie | Advisories | VulnCheck

https://www.vulncheck.com/advisories/h3-before-2.0.1-rc.18-denial-of-service-via-unbounded-chunked-cookie
github Patch Available🟡 PoC Available

Denial of Service via Unbounded Chunked Cookie Count in Session Cleanup Loop · Advisory · h3js/h3 · GitHub

https://github.com/h3js/h3/security/advisories/GHSA-q5pr-72pq-83v3

Vendor Advisories for CVE-2026-86250(1)

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

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
h3—2.0.1-rc.18—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 30× in last 7d / 55× 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 05:34 UTCEG score recompute
  2. 2026-09-19 05:34 UTCGHSA enrichment
  3. 2026-09-18 19:28 UTCEPSS rescore
  4. 2026-09-18 18:33 UTCEG score recompute
  5. 2026-09-18 18:33 UTCGHSA enrichment
  6. 2026-09-18 17:30 UTCEG score recompute
  7. 2026-09-18 17:30 UTCGHSA enrichment
  8. 2026-09-18 07:23 UTCGHSA enrichment
  9. 2026-09-17 20:21 UTCEG score recompute
  10. 2026-09-17 20:21 UTCGHSA enrichment
  11. 2026-09-17 19:32 UTCEPSS rescore
  12. 2026-09-17 05:22 UTCGHSA enrichment
  13. 2026-09-16 18:20 UTCEG score recompute
  14. 2026-09-16 18:20 UTCGHSA enrichment
  15. 2026-09-16 14:09 UTCEPSS rescore
  16. 2026-09-16 05:20 UTCEG score recompute
  17. 2026-09-16 05:20 UTCGHSA enrichment
  18. 2026-09-16 05:15 UTCEPSS rescore
  19. 2026-09-15 18:18 UTCGHSA enrichment
  20. 2026-09-15 06:47 UTCEG score recompute
  21. 2026-09-15 06:47 UTCGHSA enrichment
  22. 2026-09-15 03:12 UTCEPSS rescore
  23. 2026-09-15 03:12 UTCEPSS rescore
  24. 2026-09-14 19:45 UTCGHSA enrichment
  25. 2026-09-14 08:43 UTCGHSA enrichment
Show 30 more
  1. 2026-09-13 21:41 UTCEG score recompute
  2. 2026-09-13 21:41 UTCGHSA enrichment
  3. 2026-09-13 10:39 UTCGHSA enrichment
  4. 2026-09-12 23:37 UTCEG score recompute
  5. 2026-09-12 23:37 UTCGHSA enrichment
  6. 2026-09-12 12:35 UTCGHSA enrichment
  7. 2026-09-12 01:33 UTCEG score recompute
  8. 2026-09-12 01:33 UTCGHSA enrichment
  9. 2026-09-11 14:53 UTCEPSS rescore
  10. 2026-09-11 14:53 UTCEPSS rescore
  11. 2026-09-11 14:31 UTCEG score recompute
  12. 2026-09-11 14:31 UTCGHSA enrichment
  13. 2026-09-11 03:29 UTCGHSA enrichment
  14. 2026-09-10 16:27 UTCEG score recompute
  15. 2026-09-10 16:27 UTCGHSA enrichment
  16. 2026-09-10 05:19 UTCGHSA enrichment
  17. 2026-09-09 18:17 UTCGHSA enrichment
  18. 2026-09-09 07:16 UTCEG score recompute
  19. 2026-09-09 07:16 UTCGHSA enrichment
  20. 2026-09-08 22:01 UTCEPSS rescore
  21. 2026-09-08 20:13 UTCGHSA enrichment
  22. 2026-09-08 08:29 UTCGHSA enrichment
  23. 2026-09-07 21:27 UTCEG score recompute
  24. 2026-09-07 21:27 UTCGHSA enrichment
  25. 2026-09-07 10:25 UTCGHSA enrichment
  26. 2026-09-06 23:24 UTCEG score recompute
  27. 2026-09-06 23:24 UTCGHSA enrichment
  28. 2026-09-06 12:22 UTCEG score recompute
  29. 2026-09-06 12:12 UTCEG score recompute
  30. 2026-09-06 12:09 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-86250?
CVE-2026-86250 is a high vulnerability published on September 6, 2026. h3 versions before 2.0.1-rc.18 fail to validate the chunk count parsed from user-controlled cookie values in setChunkedCookie() and deleteChunkedCookie() functions. Attackers can send a crafted cookie header with an extremely large chunk count to trigger an O(n²) cleanup loop that hangs the server…
When was CVE-2026-86250 disclosed?
CVE-2026-86250 was first published in the National Vulnerability Database on September 6, 2026, with the most recent update on September 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-86250 actively exploited?
CVE-2026-86250 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 79.4% of all scored CVEs.
What is the CVSS score of CVE-2026-86250?
CVE-2026-86250 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-86250?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-86250, 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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