CVE-2026-15308

HIGHNVD 7.57.5—
EchelonGraph scoreHIGH confidence

Score 7.5 from GitHub Security Advisory (severity: CRITICAL) published 2026-07-09. NVD baseline CVSS 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — Patch released this week
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.5Exploit: NoneExposed: 0

A fix is available — apply it.

The incremental HTML parser (html.parser.HTMLParser) allows for CPU denial-of-service through repeated unterminated markup declarations when processing uncontrolled data.

CVSS v3
7.5
EG Score
7.5(high)
EPSS
42.3%
KEV
Not listed

Published

July 9, 2026

Last Modified

July 10, 2026

Advisory Details (3)

Auto-updated Jul 9, 2026
Upstream fix merged — awaiting tagged release. Sources: github_pr.
generic

Mailman 3 [CVE-2026-15308] Incremental HTMLParser allows CPU-exhaustion DoS via repeated unterminated markup declarations - Security-announce - python.org

https://mail.python.org/archives/list/[email protected]/thread/F6453LWKSHKCTWFLCOURWPLETNUIW2Z5/
github_pr

gh-153030: Fix quadratic complexity in incremental parsing in HTMLParser

Fix merged in python/cpython PR #153031 on 2026-07-04 — awaiting tagged release

https://github.com/python/cpython/pull/153031
generic

Another worst case quadratic complexity in HTMLParser · Issue #153030 · python/cpython · GitHub

https://github.com/python/cpython/issues/153030

Vendor Advisories for CVE-2026-15308(5)

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

Patch Availability(4)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatpython3-14-main-3.14.6-1.3.hum12026-07-10redhat
redhatpython3-13-main-3.13.14-1.3.hum12026-07-10redhat
redhatpython3-12-main-3.12.13-3.5.hum12026-07-10redhat
redhatpython3-11-main-3.11.15-5.2.hum12026-07-10redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 25× in last 7d / 25× 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. 2026-07-12 18:45 UTCEG score recompute
  2. 2026-07-12 18:45 UTCVendor advisory
  3. 2026-07-12 18:45 UTCGHSA enrichment
  4. 2026-07-12 07:11 UTCEG score recompute
  5. 2026-07-12 07:11 UTCVendor advisory
  6. 2026-07-12 07:10 UTCGHSA enrichment
  7. 2026-07-12 05:46 UTCEPSS rescore
  8. 2026-07-11 19:36 UTCEG score recompute
  9. 2026-07-11 19:36 UTCVendor advisory
  10. 2026-07-11 19:36 UTCGHSA enrichment
  11. 2026-07-11 08:27 UTCEPSS rescore
  12. 2026-07-11 08:01 UTCEG score recompute
  13. 2026-07-11 08:01 UTCVendor advisory
  14. 2026-07-11 08:01 UTCGHSA enrichment
  15. 2026-07-10 20:26 UTCEG score recompute▼ 1.20
  16. 2026-07-10 20:26 UTCVendor advisory
  17. 2026-07-10 20:26 UTCGHSA enrichment
  18. 2026-07-10 20:19 UTCNVD updateCVSS v3 → 7.5
  19. 2026-07-10 08:52 UTCEG score recompute
  20. 2026-07-10 08:51 UTCGHSA enrichment
  21. 2026-07-09 21:15 UTCEG score recompute▼ 1.30
  22. 2026-07-09 21:15 UTCGHSA enrichment
  23. 2026-07-09 19:12 UTCMITRE cvelistV5CVSS v3 → 8.7 · CVSS v4 → 8.7 · severity → HIGH
  24. 2026-07-09 17:16 UTCEG score recompute
  25. 2026-07-09 17:15 UTCMITRE cvelistV5first tracked

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-15308?
CVE-2026-15308 is a high vulnerability published on July 9, 2026. The incremental HTML parser (html.parser.HTMLParser) allows for CPU denial-of-service through repeated unterminated markup declarations when processing uncontrolled data.
When was CVE-2026-15308 disclosed?
CVE-2026-15308 was first published in the National Vulnerability Database on July 9, 2026, with the most recent update on July 10, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-15308 actively exploited?
CVE-2026-15308 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 42.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-15308?
CVE-2026-15308 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-15308?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-15308, 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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