CVE-2026-15308 PUBLISHED

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

• Edward-x (https://github.com/YLChen-007) reporter
• Serhiy Storchaka (https://github.com/serhiy-storchaka) remediation developer
• Gregory P. Smith (https://github.com/gpshead) remediation reviewer
• Seth Larson (https://github.com/sethmlarson) coordinator

• https://mail.python.org/archives/list/security-announce@python.org/thread/F6453LWKSHKCTWFLCOURWPLETNUIW2Z5/
• https://github.com/python/cpython/pull/153031
• https://github.com/python/cpython/issues/153030
• 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

• CWE-400 CWE