Vulnerability in Lepture Mistune
CVE-2026-115352
Mistune before 3.3.0 contains an algorithmic complexity vulnerability in the inline link parser that allows unauthenticated attackers to exhaust CPU by submitting long runs of unmatched '[' characters. Attackers can send small markdown payloads that trigger O(N^2) parse_link_text and parse_link_label probing, occupying rendering workers for 30+ seconds per 16 KB input.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/lepture/mistune/security/advisories/GHSA-xrpv-r66x-8p7j (vendor-advisory)
- www.vulncheck.com/advisories/mistune-before-3.3.0-quadratic-time-dos-via-unmatc… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-115352?
- CVE-2026-115352 is a high-severity vulnerability in Lepture Mistune, classified under Inefficient Algorithmic Complexity. CVSS score: 7.5/10. Published 2026-10-22.
- How severe is CVE-2026-115352?
- High severity. CVSS v3 base score is 7.5 out of 10.