Description
Mistune from 3.3.0 before 3.3.4 contains a denial of service vulnerability that allows remote attackers to exhaust CPU through quadratic-time emphasis delimiter processing. Attackers can submit small markdown documents with repeated patterns like "*a_b" to trigger an O(n²) index-fixup loop, stalling workers for seconds.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| lepture | mistune | 3.3.0 – < 3.3.4 | 3.3.4 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | mistune | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | mistune | No fix yet | — |
| Ubuntu 26.04 LTS | mistune | No fix yet | — |
| Ubuntu 24.04 LTS | mistune | No fix yet | — |
| Ubuntu 22.04 LTS | mistune | No fix yet | — |
| Ubuntu 20.04 LTS | mistune | No fix yet | — |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 18.04 LTS | mistune | No fix yet | — |
| Ubuntu 16.04 LTS | mistune | No fix yet | — |
References
- GitHub Security Advisory (GHSA-qp42-r9j6-83g9) vendor-advisory
- Patch Commit patch
- VulnCheck Advisory: Mistune 3.3.0 before 3.3.4 Quadratic-Time DoS via _process_emphasis_delimiters third-party-advisory