What’s Vulnerable › Vulnerabilities

CVE-2026-115348: Mistune before 3.3.0 Quadratic-Time DoS via parse_link_text

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-22 · updated 2026-10-23
• Weakness: CWE-400

Description

Mistune from 3.0.0 before 3.3.0 contains an algorithmic complexity vulnerability in the inline link parser's parse_link_text function that allows unauthenticated attackers to exhaust CPU with unbalanced brackets. Attackers can submit Markdown containing many unbalanced '[' or '![' characters, forcing repeated unbounded forward scans and tying up worker processes for minutes.

Affected products

• lepture mistune: from 3.0.0 before 3.3.0 — fixed in 3.3.0

How to fix

Upgrade to a fixed version: lepture mistune 3.3.0. Check the vendor advisory for mitigations.

References

• https://github.com/lepture/mistune/security/advisories/GHSA-x2gr-6qf2-fc9x
• https://www.vulncheck.com/advisories/mistune-before-3.3.0-quadratic-time-dos-via-parse-link-text

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