6.1

CVE-2026-59926: Mistune: XSS via unescaped class option in Admonition directive

Analyzed
AliasesGHSA-g97x-gvcm-x72hPYSEC-2026-2214UBUNTU-CVE-2026-59926
Published 08-07-2026Last modified 08-07-2026

Vulnerability summary

CVE-2026-59926 is a medium (CVSS 6.1) vulnerability in lepture mistune. EPSS estimates a 0.33% chance of exploitation in the next 30 days, higher than 25.8% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.3, 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 (NVD)
EPSS score
0.33%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 2 · Related 2
OPENSUSE-SU-2026:21339-1SUSE-SU-2026:22655-1

Timeline

  1. 08-07-2026
    PublishedVulnerability first disclosed.
  2. 08-07-2026
    Last modifiedVulnerability information updated.

Description

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_admonition() in src/mistune/directives/admonition.py concatenates the Admonition directive :class: option into the HTML class attribute without escaping, allowing attribute injection and cross-site scripting even when HTMLRenderer escape mode is enabled. This issue is fixed in version 3.2.1.

CVSS metrics

7 scores · 5 sources · 2 versions

EPSS trend

Probability

0.33%

Chance of exploitation in the next 30 days

Percentile

26%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.33% 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

0 found

No public exploits indexed.

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.

Debian1 product
  • mistuneAll versions (No fix recorded) | < 3.1.4-1
Lepture1 product
Mistune_project1 product
PyPI1 product
  • mistune< 3.3.0
Ubuntu1 product
  • mistuneAll versions (No fix recorded)

5 vendors · 5 products

References

9 links