CVE-2025-6069
HTMLParser quadratic complexity when processing malformed inputs
CVSS Score
4.3
EPSS Score
0.9%
EPSS Percentile
75th
The html.parser.HTMLParser class had worse-case quadratic complexity when processing certain crafted malformed inputs potentially leading to amplified denial-of-service.
| CWE | CWE-1333 |
| Vendor | python software foundation |
| Product | cpython |
| Published | Jun 17, 2025 |
| Last Updated | Apr 21, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low
Affected Versions
Python Software Foundation / CPython
0 < 3.10.19 3.11.0 < 3.11.14 3.12.0 < 3.12.12 3.13.0 < 3.13.6 3.14.0a1 < 3.14.0b3
References
github.com: https://github.com/python/cpython/issues/135462 github.com: https://github.com/python/cpython/pull/135464 github.com: https://github.com/python/cpython/commit/4455cbabf991e202185a25a631af206f60bbc949 github.com: https://github.com/python/cpython/commit/6eb6c5dbfb528bd07d77b60fd71fd05d81d45c41 github.com: https://github.com/python/cpython/commit/d851f8e258c7328814943e923a7df81bca15df4b mail.python.org: https://mail.python.org/archives/list/[email protected]/thread/K5PIYLR6EP3WR7ZOKKYQUWEDNQVUXOYM/ github.com: https://github.com/python/cpython/commit/8d1b3dfa09135affbbf27fb8babcf3c11415df49 github.com: https://github.com/python/cpython/commit/ab0893fd5c579d9cea30841680e6d35fc478afb5 github.com: https://github.com/python/cpython/commit/f3c6f882cddc8dc30320d2e73edf019e201394fc github.com: https://github.com/python/cpython/commit/fdc9d214c01cb4588f540cfa03726bbf2a33fc15
Credits
Serhiy Storchaka 🔍 Jake Howard sw0rd1ight