CVE-2026-15308
CVE-2026-15308 — Incremental HTMLParser feed() allows CPU-exhaustion DoS via repeated unterminated markup declarations
The incremental HTML parser (html.parser.HTMLParser) allows for CPU denial-of-service through repeated unterminated markup declarations when processing uncontrolled data.
Published Updated Sources: cvelistV5, PSF
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.
Exploitation
Unreported
no source claims exploitation
EPSS
1%
chance of exploitation in 30 days
CVSS base
8.7
HIGH
CISA SSVC assessment
Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.
Exploitation
None
none · proof-of-concept · active
Automatable
Yes
can an attacker script all four kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component
Affected scope
The catalog records vendors and products as separate lists, not pairs, so which product belongs to which vendor is not something this page can say.
Vendors (1)
Products (1)
Every base score collected
Sources score independently and disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Source |
|---|---|---|---|---|---|
| 8.7 | CVSS 4.0 | HIGH | — | — | cvelistV5 |
Weakness & attack patterns
- CWE-400
Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.
- T1499Endpoint Denial of Service
References
11 on the record
- mail.python.org/archives/list/[email protected]/thread/F6453LWKSHKCTWFLCOURWPLETNUIW2Z5/
vendor-advisory
- github.com/python/cpython/pull/153031
patch
- github.com/python/cpython/issues/153030
issue-tracking
- github.com/python/cpython/commit/07efb08123ba9367a7107325adb9d5626dca1ca9
patch
- github.com/python/cpython/commit/7933f4bf7131aa4140750f9404f5de0aa2969ced
patch
- github.com/python/cpython/commit/bcf98ddbc40ec9b3ee87da0124a5660b19b7e606
patch
- github.com/python/cpython/commit/e9f92ac0b298292e7ff998e52cb8ccacfb27a0bd
patch
- github.com/python/cpython/commit/785df8f743800661961528970f8598edcd291c14
patch
Elsewhere on this site
- python software foundationevery CVE for this vendor
- CWE-400other pages naming this weakness
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.