CVE-2026-15308
Medium
Elevated severity or exploit probability.
CVSS base
7.5
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS — probability of exploitation (30 days)
0.6%
49.1th percentile
CISA KEV
Not listed
Weakness / dates
CWE-400
Published 2026-07-09 · modified 2026-08-20
CVSS breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
| Attack Vector | N | Network |
| Attack Complexity | L | Low |
| Privileges Required | N | None |
| User Interaction | N | None |
| Scope | U | Unchanged |
| Confidentiality | N | None |
| Integrity | N | None |
| Availability | H | High |
Timeline
- 2026-07-09 — Published (NVD)
- 2026-08-20 — Last modified (NVD)
Description
The incremental HTML parser (html.parser.HTMLParser) allows for CPU denial-of-service through repeated unterminated markup declarations when processing uncontrolled data.
Affected
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
- https://github.com/python/cpython/commit/c2390b9376e35a701ed3acc597b8fc87546c9b00
- 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