Incremental HTMLParser feed() allows CPU-exhaustion DoS via repeated unterminated markup declarations
Summary
| CVE | CVE-2026-15308 |
|---|---|
| State | PUBLISHED |
| Assigner | PSF |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-07-09 17:16:58 UTC |
| Updated | 2026-07-10 20:07:52 UTC |
| Description | The incremental HTML parser (html.parser.HTMLParser) allows for CPU denial-of-service through repeated unterminated markup declarations when processing uncontrolled data. |
Risk And Classification
Primary CVSS: v4.0 8.7 HIGH from [email protected]
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
EPSS: 0.005530000 probability, percentile 0.423180000 (date 2026-07-13)
Problem Types: CWE-400 | NVD-CWE-noinfo | CWE-400 CWE-400
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 8.7 | HIGH | 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/C... |
| 4.0 | CNA | CVSS | 8.7 | HIGH | 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 |
| 3.1 | [email protected] | Primary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
CVSS v4.0 Breakdown
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
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD Known Affected Configurations (CPE 2.3)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Python Software Foundation | CPython | affected 3.15.0 python | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| mail.python.org/archives/list/[email protected]/thread/F6453LWKSHK... | [email protected] | mail.python.org | Mailing List |
| github.com/python/cpython/commit/07efb08123ba9367a7107325adb9d5626dca1ca9 | [email protected] | github.com | Patch |
| github.com/python/cpython/commit/bcf98ddbc40ec9b3ee87da0124a5660b19b7e606 | [email protected] | github.com | Patch |
| github.com/python/cpython/commit/7933f4bf7131aa4140750f9404f5de0aa2969ced | [email protected] | github.com | Patch |
| github.com/python/cpython/commit/e9f92ac0b298292e7ff998e52cb8ccacfb27a0bd | [email protected] | github.com | Patch |
| github.com/python/cpython/pull/153031 | [email protected] | github.com | Issue Tracking, Patch |
| github.com/python/cpython/issues/153030 | [email protected] | github.com | Patch |
| www.openwall.com/lists/oss-security/2026/07/09/4 | af854a3a-2127-422b-91ae-364da2661108 | www.openwall.com | Third Party Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Edward-x (https://github.com/YLChen-007) (en)
CNA: Serhiy Storchaka (https://github.com/serhiy-storchaka) (en)
CNA: Gregory P. Smith (https://github.com/gpshead) (en)
CNA: Seth Larson (https://github.com/sethmlarson) (en)