VulnerabilityAnalyzed
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.
HIGH 8.7EPSS 0.64%
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.64%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
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
- 8.7 HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 0.64% probability · 49th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-400
- Affected
- python/python
- Source
- cna@python.org
References
- https://github.com/python/cpython/commit/07efb08123ba9367a7107325adb9d5626dca1ca9Patch
- https://github.com/python/cpython/commit/1e7956f1a722df9aabc509c30f8fbdc3a2b4fdc7Patch
- https://github.com/python/cpython/commit/785df8f743800661961528970f8598edcd291c14Patch
- https://github.com/python/cpython/commit/7933f4bf7131aa4140750f9404f5de0aa2969cedPatch
- https://github.com/python/cpython/commit/bcf98ddbc40ec9b3ee87da0124a5660b19b7e606Patch
- https://github.com/python/cpython/commit/c2390b9376e35a701ed3acc597b8fc87546c9b00Patch
- https://github.com/python/cpython/commit/e9f92ac0b298292e7ff998e52cb8ccacfb27a0bdPatch
- https://github.com/python/cpython/issues/153030Patch
- https://github.com/python/cpython/pull/153031Issue Tracking, Patch
- https://mail.python.org/archives/list/security-announce@python.org/thread/F6453LWKSHKCTWFLCOURWPLETNUIW2Z5/Mailing List
- http://www.openwall.com/lists/oss-security/2026/07/09/4Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.