7.5

CVE-2026-76098: Mistune has Denial of Service — RecursionError via Excessive Emphasis Markers in Markdown

Deferred
AliasesGHSA-6m44-fpc8-c3rqPYSEC-2026-3863UBUNTU-CVE-2026-76098
Published 24-08-2026Last modified 24-08-2026

Vulnerability summary

CVE-2026-76098 is a high (CVSS 7.5) Uncontrolled Recursion vulnerability in lepture mistune. EPSS estimates a 0.49% chance of exploitation in the next 30 days, higher than 42% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 7.5 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 0% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?
CVSS score
7.5/10
010
High · v3.1 (CVE.org)
EPSS score
0.49%
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

Timeline

  1. 24-08-2026
    PublishedVulnerability first disclosed.
  2. 24-08-2026
    Last modifiedVulnerability information updated.

Description

Mistune is a Python Markdown parser with renderers and plugins. Versions 3.3.0 through 3.3.2 are vulnerable to DoS through deeply nested tokens. HTML rendering creates deeply nested emphasis tokens from consecutive asterisk characters, and recursive rendering in HTMLRenderer.render_token() can exceed Python's recursion limit and raise RecursionError, allowing crafted Markdown to crash a parsing process. This issue is fixed in version 3.3.3

CVSS metrics

5 scores · 5 sources · 1 version

EPSS trend

Probability

0.49%

Chance of exploitation in the next 30 days

Percentile

42%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.49% 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, no user interaction (CVSS vector). Other conditions: not stated in public data.

Debian1 product
  • mistuneAll versions (No fix recorded)
Lepture1 product
PyPI1 product
  • mistune≥ 3.3.0, < 3.3.3
Ubuntu1 product
  • mistuneAll versions (No fix recorded)

4 vendors · 4 products

References

14 links
Show all 14 references