CVE catalog
CVE-2026-115347
mistune: CVE-2026-115347
- 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
- 0.41% · Oct 25, 2026
Mistune before 3.3.0 contains an inefficient algorithmic complexity vulnerability in parse_link_text that allows remote attackers to cause denial of service through unbalanced square brackets. Attackers can submit markdown containing long runs of unmatched brackets to mistune.html(), triggering repeated forward scans that stall worker processes for minutes.
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-f32h-38gf-rg5r]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-115347]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-115347]
- [https://osv.dev/vulnerability/UBUNTU-CVE-2026-115347]
- [https://security-tracker.debian.org/tracker/CVE-2026-115347]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-115347.json]
- [https://www.vulncheck.com/advisories/mistune-before-3.3.0-quadratic-denial-of-service-via-parse-link-text]
[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX]