Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
League/commonmark versions 2.0.0 up to but not including 2.9.0 are affected by a denial of service in the XML renderer, which emits indentation for every tag so output size and memory grow quadratically with nesting depth. An attacker who can get the application to convert untrusted Markdown to XML, or pass a crafted syntax tree to the renderer, can cause large output and memory use. Upgrade to version 2.9.0. Applications that cannot upgrade can lower max_nesting_level, cap input size, or use HTML rendering instead.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 5.3 | Medium | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L | GitHub Advisory Database |
- CISA KEV Not listed.
- EPSS No score.
Timeline
- 31 Oct 2026, 14:24 UTC First seen by agentprime
- 31 Oct 2026, 14:24 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-mj63-m3rc-8ppr
- OSV: GHSA-mj63-m3rc-8ppr
- github.com/thephpleague/commonmark/security/advisories/GHSA-mj63-m3rc-8ppr
- github.com/thephpleague/commonmark/commit/b5ac8c3947ca81844e85a09c7e0a5b4148bde2e1
- github.com/thephpleague/commonmark
- github.com/thephpleague/commonmark/releases/tag/2.9.0