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CVE-2026-44897

26
FAUCET Score

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, HTMLRenderer.heading() builds the opening <hN> tag by string-concatenating the id attribute value directly into the HTML — with no call to escape(), safe_entity(), or any other sanitisation function. A double-quote character " in the id value terminates the attribute, allowing an attacker to inject arbitrary additional attributes (event handlers, src=, href=, etc.) into the heading element. This vulnerability is fixed in 3.2.1.

First published: May 26, 2026Last modified: May 26, 2026

Impacted Technologies

VendorProductVersion(s)CPE
< 3.2.1CPE matchmatch criteria
cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.1MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
2.7
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.23%
Probability of exploitation in next 30 days
EPSS Percentile
13.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0023 is in the 14th percentile among its peer group of 26,234 CVEs.

Social Chatter

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

Media Mentions

No media coverage found for this CVE.

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

Remediation

Patch Available

Vendor Patches (2)

pippatch availablevia ghsa
Product: mistuneFixed in: 3.2.1
github_advisoryvendor investigatingvia nvd_reference
View patch

Vendor Advisories (2)

microsoft2026-May/CVE-2026-44897Moderate

Mistune Heading ID Attribute Injection XSS

May 12, 2026
pipGHSA-v87v-83h2-53w7medium

Mistune Heading ID Attribute has Injection XSS

May 9, 2026

References

github.com / lepture/mistune/releases/tag/v3.2.1
ProductRelease Notes
github.com / lepture/mistune/security/advisories/GHSA-v87v-83h2-53w7
ExploitVendor Advisory