6.1

CVE-2026-44897: Mistune Heading ID Attribute Injection XSS

Analyzed
AliasesGHSA-v87v-83h2-53w7PYSEC-2026-2207UBUNTU-CVE-2026-44897
Published 26-05-2026Last modified 01-06-2026

Vulnerability summary

CVE-2026-44897 is a medium (CVSS 6.1) vulnerability in lepture mistune. EPSS estimates a 0.23% chance of exploitation in the next 30 days, higher than 13.6% of scored vulnerabilities. 1 public exploit is recorded.

Priority
Routine

Not severe (CVSS 6.1, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
6.1/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.23%
0%100%
Low · -0.04 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits1github

Advisory lineage

Upstream 0 · Downstream 1 · Related 2
OPENSUSE-SU-2026:10761-1CGA-94FX-GGG6-64V9

Timeline

  1. 26-05-2026
    PublishedVulnerability first disclosed.
  2. 01-06-2026
    Last modifiedVulnerability information updated.

Description

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.

CVSS metrics

7 scores · 7 sources · 1 version

EPSS trend

Probability

0.23%

Chance of exploitation in the next 30 days

Percentile

14%

Versus all other CVEs

30-day change

Decrease -0.04 pp

From 0.27% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

1 found
  • githubUnverified

    Mistune

    Maturity: poc

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, user interaction (CVSS vector). Other conditions: not stated in public data.

Chainguard2 products
  • datahub-ingestion-fips< 1.5.0.1-r2
  • kubeflow-pipelines-visualization-server< 2.16.1-r2
Ubuntu2 products
  • mistuneAll versions (No fix recorded)
  • mistune0All versions (No fix recorded)
Debian1 product
  • mistuneAll versions (No fix recorded)
Lepture1 product
Mistune_project1 product
PyPI1 product
  • mistune< 3.2.1
Wolfi1 product
  • kubeflow-pipelines-visualization-server< 2.16.1-r2

7 vendors · 9 products

References

8 links