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.

CVSS 4.0

8.7CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS 3.1

7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

0.6% chance of exploitation in the next 30 days; higher than 50% of CVEs (scores of 2026-10-25)

CWE

CWE-400

Published

2026-07-09

Modified

2026-10-25

Record from

the NVD, synced 2026-10-25

Affected

• python:python

References

• https://github.com/python/cpython/commit/07efb08123ba9367a7107325adb9d5626dca1ca9
• https://github.com/python/cpython/commit/1e7956f1a722df9aabc509c30f8fbdc3a2b4fdc7
• https://github.com/python/cpython/commit/785df8f743800661961528970f8598edcd291c14
• https://github.com/python/cpython/commit/7933f4bf7131aa4140750f9404f5de0aa2969ced
• https://github.com/python/cpython/commit/bcf98ddbc40ec9b3ee87da0124a5660b19b7e606

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