High 7.5Published Oct 22, 2026

CVE-2026-115352Mistune before 3.3.0 Quadratic-Time DoS via Unmatched Brackets in Inline Parser

Updated under an hour ago (Oct 26, 2026, 11:50 PM ET)

Does this affect you?

It affects lepture mistune. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.44%, higher than 38% of scored CVEs.

Do this next

Start free and add your stack

Free account, 1 product

Every CVE for lepture mistune

Exploited in the last 30 days

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.

CVSS: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-407
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.44% (percentile 38)
Assigned by: VulnCheck
NVD analysis: Deferred
Record last updated: Oct 23, 2026
First seen by InfoSec Signals: Oct 22, 2026

Affected products

Affected products

lepture mistune lepture:mistune (from the name)	before 3.3.0; 3.3.0 not affected	CNA record

References

References

https://github.com/lepture/mistune/security/advisories/GHSA-xrpv-r66x-8p7j	vendor-advisory
https://www.vulncheck.com/advisories/mistune-before-3.3.0-quadratic-time-dos-via-unmatched-brackets-in-inline-parser	third-party-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.