CVE-2026-44436

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 80% of all CVEs by exploit prediction. 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
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.

Quicly is an IETF QUIC protocol implementation intended primarily for use within the H2O HTTP server. Prior to commit 8b178e6, Quicly is vulnerable to a Denial of Service attack through connection state corruption. In QUIC Invariants, the maximum length of a Connection ID is 255 bytes, while QUIC version 1 further restricts the maximum to 20 bytes. Quicly implements QUIC version 1 and therefore its CID buffers are limited to 20 bytes. However, to be able to respond to unknown versions of QUIC, its packet decoder accepts Connection IDs of up to 255 bytes. As its CID buffers are merely 20 bytes long, Quicly must reject QUIC version 1 packets with Connection IDs longer than that. The command line tool bundled with Quicly has had that check, however the library itself lacked such enforcement. As a consequence, when used by applications that lack their own enforcement, the connection state becoming inconsistent to buffer overrun. Fortunately, the overflow stops within the allocated chunk of memory, but nevertheless, the bug leads to assertion failures. This issue has been fixed by commit 8b178e6.

CVSS v3
7.5
EG Score
7.5(medium)
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
20%
KEV
Not listed

Published

July 16, 2026

Last Modified

July 21, 2026

Advisory Details (1)

Auto-updated Jul 16, 2026
Patch available. Sources: github.
github Patch Available

connection state corruption · Advisory · h2o/quicly · GitHub

https://github.com/h2o/quicly/security/advisories/GHSA-v55w-59qx-2v78

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 14× in last 7d / 24× 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. 2026-07-28 17:28 UTCEG score recompute
  2. 2026-07-28 15:36 UTCEPSS rescore
  3. 2026-07-27 15:16 UTCEG score recompute
  4. 2026-07-27 14:13 UTCEPSS rescore
  5. 2026-07-27 00:30 UTCEG score recompute
  6. 2026-07-26 14:54 UTCEPSS rescore
  7. 2026-07-26 14:54 UTCEPSS rescore
  8. 2026-07-26 11:23 UTCEG score recompute
  9. 2026-07-25 14:18 UTCEPSS rescore
  10. 2026-07-24 14:17 UTCEPSS rescore
  11. 2026-07-23 14:18 UTCEPSS rescore
  12. 2026-07-23 03:15 UTCEG score recompute
  13. 2026-07-23 00:24 UTCEG score recompute
  14. 2026-07-22 14:08 UTCEPSS rescore
  15. 2026-07-21 15:24 UTCEPSS rescore
  16. 2026-07-20 17:08 UTCEPSS rescore
  17. 2026-07-19 14:31 UTCEPSS rescore
  18. 2026-07-19 02:32 UTCEG score recompute
  19. 2026-07-19 02:29 UTCEPSS rescore
  20. 2026-07-18 10:04 UTCEPSS rescore
  21. 2026-07-17 12:02 UTCEG score recompute
  22. 2026-07-17 11:02 UTCEG score recompute
  23. 2026-07-16 23:43 UTCEG score recompute
  24. 2026-07-16 23:43 UTCNVD updatefirst tracked

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Frequently asked(5)

What is CVE-2026-44436?
CVE-2026-44436 is a high vulnerability published on July 16, 2026. Quicly is an IETF QUIC protocol implementation intended primarily for use within the H2O HTTP server. Prior to commit 8b178e6, Quicly is vulnerable to a Denial of Service attack through connection state corruption. In QUIC Invariants, the maximum length of a Connection ID is 255 bytes, while QUIC…
When was CVE-2026-44436 disclosed?
CVE-2026-44436 was first published in the National Vulnerability Database on July 16, 2026, with the most recent update on July 21, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-44436 actively exploited?
CVE-2026-44436 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 79.9% of all scored CVEs.
What is the CVSS score of CVE-2026-44436?
CVE-2026-44436 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-44436?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-44436, 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.

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