CVE-2026-12523

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 79% 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.

Summary

Cloudflare quiche's HTTP/3 layer was discovered to be vulnerable to resource exhaustion (i.e., memory) by means of specially crafted HTTP/3 frames.

Impact

HTTP/3 defines multiple frame types to support HTTP message exchanges and connection management. Each frame has a length and a payload whose length depends on the frame type. quiche was found to be vulnerable when parsing some frame types to pre-allocating memory based on the declared length. An attacker would not need to send the number of declared bytes to trigger this issue.

In addition, quiche was found to not apply QPACK decompression limits correctly. This could allow an attacker to send specially crafted HEADERS frames that would cause more memory commitment than otherwise advertised by MAX_FIELD_SECTION_SIZE (configured by set_max_field_section_size()).

Mitigation:

*

Users are requested to upgrade to quiche 0.29.3 which is the earliest version containing the fix for this issue.

Credits: Disclosed responsibly by Sébastien Féry

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
21%
KEV
Not listed

Published

July 14, 2026

Last Modified

July 15, 2026

Advisory Details (1)

Auto-updated Jul 15, 2026
Patch available. Sources: github.
github Patch Available

Resource exhaustion in HTTP/3 and QPACK · Advisory · cloudflare/quiche · GitHub

https://github.com/cloudflare/quiche/security/advisories/GHSA-4fgf-9xrr-88gf

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 12× in last 7d / 20× 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. 2026-07-27 20:56 UTCEG score recompute
  2. 2026-07-27 14:13 UTCEPSS rescore
  3. 2026-07-26 22:50 UTCEG score recompute
  4. 2026-07-26 14:54 UTCEPSS rescore
  5. 2026-07-26 14:54 UTCEPSS rescore
  6. 2026-07-26 11:45 UTCEG score recompute
  7. 2026-07-25 14:17 UTCEPSS rescore
  8. 2026-07-24 14:17 UTCEPSS rescore
  9. 2026-07-23 14:18 UTCEPSS rescore
  10. 2026-07-23 03:05 UTCEG score recompute
  11. 2026-07-22 14:08 UTCEPSS rescore
  12. 2026-07-21 15:24 UTCEPSS rescore
  13. 2026-07-20 17:08 UTCEPSS rescore
  14. 2026-07-19 14:30 UTCEPSS rescore
  15. 2026-07-19 02:28 UTCEPSS rescore
  16. 2026-07-18 10:04 UTCEPSS rescore
  17. 2026-07-16 17:02 UTCEPSS rescore
  18. 2026-07-15 16:57 UTCEPSS rescore
  19. 2026-07-14 16:11 UTCEG score recompute
  20. 2026-07-14 16:10 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-12523?
CVE-2026-12523 is a high vulnerability published on July 14, 2026. Summary Cloudflare quiche's HTTP/3 layer was discovered to be vulnerable to resource exhaustion (i.e., memory) by means of specially crafted HTTP/3 frames. Impact HTTP/3 defines multiple frame types to support HTTP message exchanges and connection management. Each frame has a length and a payload…
When was CVE-2026-12523 disclosed?
CVE-2026-12523 was first published in the National Vulnerability Database on July 14, 2026, with the most recent update on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-12523 actively exploited?
CVE-2026-12523 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 78.6% of all scored CVEs.
What is the CVSS score of CVE-2026-12523?
CVE-2026-12523 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-12523?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-12523, 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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