Resource exhaustion in Python
CVE-2026-15308
The incremental HTML parser (html.parser.HTMLParser) allows for CPU denial-of-service through repeated unterminated markup declarations when processing uncontrolled data.
Vulnerability class: DoS (Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.006 (48.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 49th percentile — 48.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000
Affected products
- Python — versions 3.15.0
- Python Software Foundation Cpython — versions 3.14.0, 0, 3.13.0
Weakness classification (CWE)
References
- github.com/python/cpython/issues/153030 (issue-tracking, Patch)
- github.com/python/cpython/pull/153031 (Patch, patch, Issue Tracking)
- mail.python.org/archives/list/security-announce@python.org/thread/F6453LWKSHKCT… (vendor-advisory, Mailing List)
- github.com/python/cpython/commit/07efb08123ba9367a7107325adb9d5626dca1ca9 (Patch, patch)
- github.com/python/cpython/commit/7933f4bf7131aa4140750f9404f5de0aa2969ced (Patch, patch)
- github.com/python/cpython/commit/bcf98ddbc40ec9b3ee87da0124a5660b19b7e606 (Patch, patch)
- github.com/python/cpython/commit/e9f92ac0b298292e7ff998e52cb8ccacfb27a0bd (Patch, patch)
- af854a3a-2127-422b-91ae-364da2661108 (Third Party Advisory)
- github.com/python/cpython/commit/785df8f743800661961528970f8598edcd291c14 (Patch, patch)
- github.com/python/cpython/commit/1e7956f1a722df9aabc509c30f8fbdc3a2b4fdc7 (Patch, patch)
Frequently asked questions
- What is CVE-2026-15308?
- CVE-2026-15308 is a high-severity vulnerability in Python, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-07-09.
- How severe is CVE-2026-15308?
- High severity. CVSS v3 base score is 7.5 out of 10.