High 7.5Published Oct 22, 2026

CVE-2026-115349Mistune 3.0.0 before 3.3.0 Denial of Service via Nested Bracket Parsing

Updated under an hour ago (Oct 28, 2026, 5:10 AM ET)

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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 0.34%, higher than 28% of scored CVEs.

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Every CVE for lepture mistune

Exploited in the last 30 days

Mistune from 3.0.0 before 3.3.0 contains an algorithmic complexity denial of service vulnerability in the parse_link_text function in src/mistune/helpers.py. Attackers can submit markdown with deeply nested square brackets triggering quadratic parsing time, exhausting server CPU with small crafted requests.

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-1333
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.34% (percentile 28)
Assigned by: VulnCheck
NVD analysis: Deferred
Record last updated: Oct 26, 2026
First seen by InfoSec Signals: Oct 22, 2026

Affected products

Affected products

lepture mistune lepture:mistune (from the name)	from 3.0.0 before 3.3.0; 3.3.0 not affected	CNA record

References

References

https://github.com/lepture/mistune/security/advisories/GHSA-3q64-rw38-243v	vendor-advisory
https://www.vulncheck.com/advisories/mistune-3.0.0-before-3.3.0-denial-of-service-via-nested-bracket-parsing	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.