CVE catalog
CVE-2026-115349
mistune: CVE-2026-115349
- Severity
- High · CVSS 8.7
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - Published
- Source
- [NVD] · [CVE record]
- EPSS
- 0.34% · Oct 25, 2026
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.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | mistune | sid | 3.4.0-1 | fixed |
| Debian | mistune | forky | 3.1.4-1 | vulnerable |
| Debian | mistune | trixie | 3.1.3-1 | vulnerable |
| Debian | mistune | bookworm | 2.0.4-1 | vulnerable |
| Ubuntu | mistune | 16.04 | 0.6-2 | vulnerable |
| Ubuntu | mistune | 16.04 | 0.7.1-1 | vulnerable |
| Ubuntu | mistune | 18.04 | 0.7.4-1 | vulnerable |
| Ubuntu | mistune | 18.04 | 0.8-1 | vulnerable |
| Ubuntu | mistune | 18.04 | 0.8.1-1 | vulnerable |
| Ubuntu | mistune | 18.04 | 0.8.3-2 | vulnerable |
| Ubuntu | mistune | 20.04 | 0.8.4-1 | vulnerable |
| Ubuntu | mistune | 20.04 | 0.8.4-2 | vulnerable |
| Ubuntu | mistune | 22.04 | 0.8.4-4 | vulnerable |
| Ubuntu | mistune | 22.04 | 0.8.4-5 | vulnerable |
| Ubuntu | mistune | 22.04 | 2.0.0-1+really0.8.4-1 | vulnerable |
| Ubuntu | mistune | 24.04 | 2.0.4-2 | vulnerable |
| Ubuntu | mistune | 24.04 | 3.0.2-1 | vulnerable |
| Ubuntu | mistune | 26.10 | 3.1.4-1 | vulnerable |
| Ubuntu | mistune | 26.04 | 3.1.3-1 | vulnerable |
| Ubuntu | mistune | 26.04 | 3.1.4-1 | vulnerable |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | mistune | source | sid | 3.3.4-1 | not yet assigned | Not reported | Not reported |
| Debian | mistune | source | forky | (unfixed) | not yet assigned | Not reported | Not reported |
| Debian | mistune | source | trixie | (unfixed) | not yet assigned | Not reported | Not reported |
| Debian | mistune | source | bookworm | (unfixed) | not yet assigned | Not reported | Not reported |
Notes
[trixie] mistune: Minor issue
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [python3-mistune]Affected
Source package: [mistune]
Details (2)
2.0.4-1· all · bookwormAffected
dsa · mistune · debian · bookworm; dsa · mistune · debian · 12
2.0.4-1· all · bookwormAffected
dsa · mistune · debian · bookworm; dsa · mistune · debian · 12
[Debian 13 (Trixie)]
- [python3-mistune]Affected
Source package: [mistune]
Details (2)
3.1.3-1· all · trixieAffected
dsa · mistune · debian · 13
3.1.3-1· all · trixieAffected
dsa · mistune · debian · 13
Observed:
References
- [https://github.com/lepture/mistune/security/advisories/GHSA-3q64-rw38-243v]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-115349]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-115349]
- [https://osv.dev/vulnerability/UBUNTU-CVE-2026-115349]
- [https://security-tracker.debian.org/tracker/CVE-2026-115349]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-115349.json]
- [https://www.vulncheck.com/advisories/mistune-3.0.0-before-3.3.0-denial-of-service-via-nested-bracket-parsing]
[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX]