CVE-2026-15308

EUVD-2026-42638
The incremental HTML parser (html.parser.HTMLParser) allows for CPU
denial-of-service through repeated unterminated markup declarations when
processing uncontrolled data.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
PSFCNA
8.7 HIGH
NETWORK
LOW
NONE
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Base Score
CVSS 3.x
EPSS Score
Percentile: Unknown
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources.
VendorProductVersionSource
pythoncpython
𝑥
< 3.15.0
CNA
Common Weakness Enumeration
References
https://github.com/python/cpython/commit/07efb08123ba9367a7107325adb9d5626dca1ca9
https://github.com/python/cpython/commit/7933f4bf7131aa4140750f9404f5de0aa2969ced
https://github.com/python/cpython/commit/bcf98ddbc40ec9b3ee87da0124a5660b19b7e606
https://github.com/python/cpython/commit/e9f92ac0b298292e7ff998e52cb8ccacfb27a0bd
https://github.com/python/cpython/issues/153030
https://github.com/python/cpython/pull/153031
https://mail.python.org/archives/list/security-announce@python.org/thread/F6453LWKSHKCTWFLCOURWPLETNUIW2Z5/
http://www.openwall.com/lists/oss-security/2026/07/09/4