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CVE-2026-15308

38
FAUCET Score

The incremental HTML parser (html.parser.HTMLParser) allows for CPU denial-of-service through repeated unterminated markup declarations when processing uncontrolled data.

First published: Jul 9, 2026Last modified: Jul 23, 2026

Impacted Technologies

VendorProductVersion(s)CPE
< 3.15.0CPE matchmatch criteria
cpe:2.3:a:python:python:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 4.0

8.7HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
VS Confidentiality
HIGH
VS Integrity
HIGH
VS Availability
HIGH
SS Confidentiality
HIGH
SS Integrity
HIGH
SS Availability
HIGH
Exploit Maturity
NOT_DEFINED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
0.55%
Probability of exploitation in next 30 days
EPSS Percentile
42.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0055 is in the 20th percentile among its peer group of 51,551 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Advisories (1)

microsoft2026-Jul/CVE-2026-15308Important

Incremental HTMLParser feed() allows CPU-exhaustion DoS via repeated unterminated markup declarations

Jul 14, 2026

References

openwall.com / lists/oss-security/2026/07/09/4
Third Party Advisory
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/issues/153030
Patch
github.com / python/cpython/pull/153031
Issue TrackingPatch
mail.python.org / archives/list/[email protected]/thread/F6453LWKSHKCTWFLCOURWPLETNUIW2Z5
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