CVE-2026-15308
What it is
The incremental HTML parser (html.parser.HTMLParser) allows for CPU denial-of-service through repeated unterminated markup declarations when processing uncontrolled data.
At a glance
- Exploitability
- Can be exploited over the network without logging in. High risk of service disruption.
- Exploit odds
- 0.6% chance of exploitation in the next 30 days (EPSS).
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: 0.6% in the next 30 days (EPSS).
- Severity: 8.7 HIGH (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Exploit probability
- 0.6% · EPSS, next 30 days
- Weakness
- CWE-400 · Uncontrolled resource consumption
- Record status
- Modified
Affected
- Python < 3.10.21
- Python < 3.11.16
- Python < 3.12.14
- Python < 3.13.15
- Python < 3.14.7
- Python 3.15.0
Attack profile CVSS 4.0 · 8.7
- Attack vector
- Network
- Complexity
- Low
- Attack requirements
- None
- Privileges needed
- None
- User interaction
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Raw vector
CVSS: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/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2026-15308.md and follow it. Check whether this project is affected by CVE-2026-15308. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
Fix and advisories
- 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
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/[email protected]/thread/F6453LWKSHKCTWFLCOURWPLETNUIW2Z5/
- http://www.openwall.com/lists/oss-security/2026/07/09/4
- https://cert-portal.siemens.com/productcert/html/ssa-457936.html