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
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 7.5Exploit: None knownExposed: 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)
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%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
43%
KEV
Not listed

Published

July 9, 2026

Last Modified

July 23, 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(14)

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

Patch Availability(12)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatrhui5/rhua-rhel9:17847950762026-07-23redhat
redhatpython3.14-0:3.14.5-1.el9_8.12026-07-20redhat
redhatpython3.14-0:3.14.5-1.el10_2.12026-07-16redhat
redhatpython3.9-0:3.9.25-7.el9_8.22026-07-15redhat
redhatpython3.12-0:3.12.13-3.el8_102026-07-15redhat
redhatpython3.12-0:3.12.13-3.el9_8.12026-07-15redhat
redhatpython3.12-0:3.12.13-2.el10_2.12026-07-14redhat
redhatpython3-0:3.6.8-77.el8_102026-07-14redhat
redhatpython3-11-main-3.11.15-5.2.hum12026-07-10redhat
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

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 17× in last 7d / 63× 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 04:20 UTCVendor advisory
  2. 2026-07-27 04:20 UTCGHSA enrichment
  3. 2026-07-26 16:43 UTCEG score recompute
  4. 2026-07-26 16:43 UTCVendor advisory
  5. 2026-07-26 16:43 UTCGHSA enrichment
  6. 2026-07-26 14:54 UTCEPSS rescore
  7. 2026-07-26 14:54 UTCEPSS rescore
  8. 2026-07-26 05:07 UTCEG score recompute
  9. 2026-07-26 05:07 UTCVendor advisory
  10. 2026-07-26 05:07 UTCGHSA enrichment
  11. 2026-07-25 14:17 UTCEPSS rescore
  12. 2026-07-24 14:17 UTCEPSS rescore
  13. 2026-07-23 14:18 UTCEPSS rescore
  14. 2026-07-23 03:05 UTCEG score recompute
  15. 2026-07-22 14:08 UTCEPSS rescore
  16. 2026-07-21 15:24 UTCEPSS rescore
  17. 2026-07-20 17:08 UTCEPSS rescore
  18. 2026-07-19 14:30 UTCEPSS rescore
  19. 2026-07-19 02:28 UTCEPSS rescore
  20. 2026-07-18 10:04 UTCEPSS rescore
  21. 2026-07-17 03:08 UTCVendor advisory
  22. 2026-07-17 03:08 UTCGHSA enrichment
  23. 2026-07-16 17:02 UTCEPSS rescore
  24. 2026-07-16 15:33 UTCVendor advisory
  25. 2026-07-16 15:33 UTCGHSA enrichment
Show 38 more
  1. 2026-07-16 03:53 UTCVendor advisory
  2. 2026-07-16 03:53 UTCGHSA enrichment
  3. 2026-07-15 16:57 UTCEPSS rescore
  4. 2026-07-15 16:18 UTCVendor advisory
  5. 2026-07-15 16:18 UTCGHSA enrichment
  6. 2026-07-15 04:44 UTCVendor advisory
  7. 2026-07-15 04:44 UTCGHSA enrichment
  8. 2026-07-15 02:00 UTCEPSS rescore
  9. 2026-07-14 17:08 UTCVendor advisory
  10. 2026-07-14 17:08 UTCGHSA enrichment
  11. 2026-07-14 05:32 UTCVendor advisory
  12. 2026-07-14 05:32 UTCGHSA enrichment
  13. 2026-07-13 22:30 UTCEPSS rescore
  14. 2026-07-13 17:58 UTCVendor advisory
  15. 2026-07-13 17:58 UTCGHSA enrichment
  16. 2026-07-13 06:24 UTCVendor advisory
  17. 2026-07-13 06:23 UTCGHSA enrichment
  18. 2026-07-13 06:12 UTCEPSS rescore
  19. 2026-07-12 18:45 UTCVendor advisory
  20. 2026-07-12 18:45 UTCGHSA enrichment
  21. 2026-07-12 07:11 UTCVendor advisory
  22. 2026-07-12 07:10 UTCGHSA enrichment
  23. 2026-07-12 05:46 UTCEPSS rescore
  24. 2026-07-11 19:36 UTCVendor advisory
  25. 2026-07-11 19:36 UTCGHSA enrichment
  26. 2026-07-11 08:27 UTCEPSS rescore
  27. 2026-07-11 08:01 UTCVendor advisory
  28. 2026-07-11 08:01 UTCGHSA enrichment
  29. 2026-07-10 20:26 UTCEG score recompute▼ 1.20
  30. 2026-07-10 20:26 UTCVendor advisory
  31. 2026-07-10 20:26 UTCGHSA enrichment
  32. 2026-07-10 20:19 UTCNVD updateCVSS v3 → 7.5
  33. 2026-07-10 08:51 UTCGHSA enrichment
  34. 2026-07-09 21:15 UTCEG score recompute▼ 1.30
  35. 2026-07-09 21:15 UTCGHSA enrichment
  36. 2026-07-09 19:12 UTCMITRE cvelistV5CVSS v3 → 8.7 · CVSS v4 → 8.7 · severity → HIGH
  37. 2026-07-09 17:16 UTCEG score recompute
  38. 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 23, 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 1% probability of exploitation in the next 30 days, which ranks it in the top 57.2% of all scored CVEs.
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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