Vulnerability · Published Oct 22, 2026 · Assigned by VulnCheck

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

High 7.5

In plain English

A high-severity uncontrolled resource consumption in mistune from lepture. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 38% of all known vulnerabilities).

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.4%top 61.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	mistune	no fix listed	DEBIAN-CVE-2026-115348
Debian:13	mistune	no fix listed	DEBIAN-CVE-2026-115348
Debian:14	mistune	no fix listed	DEBIAN-CVE-2026-115348
Ubuntu:22.04:LTS	mistune	no fix listed	UBUNTU-CVE-2026-115348
Ubuntu:24.04:LTS	mistune	no fix listed	UBUNTU-CVE-2026-115348
Ubuntu:26.04:LTS	mistune	no fix listed	UBUNTU-CVE-2026-115348
Ubuntu:26.10	mistune	no fix listed	UBUNTU-CVE-2026-115348

Affected products (as reported)

Vendor	Product	Versions
lepture	mistune	3.0.0 – before 3.3.0

Weakness: CWE-400 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

GitHub Security Advisory (GHSA-x2gr-6qf2-fc9x) vendor-advisory
VulnCheck Advisory: Mistune before 3.3.0 Quadratic-Time DoS via parse_link_text third-party-advisory