Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
League/commonmark versions from 1.5.0 before 2.9.0 are affected by a denial of service in the Attributes extension, where a run of adjacent inline attribute blocks at the start of a block takes quadratic time to process. An unauthenticated attacker who can submit input to a site using the extension can cause very high CPU use with a small input of about 32 KB. Upgrade to league/commonmark 2.9.0. If upgrading is not possible, disable the Attributes extension for untrusted input or enforce a small maximum input length before conversion.
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 |
|---|---|---|---|---|
| 7.5 | High | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | GitHub Advisory Database |
- CISA KEV Not listed.
- EPSS No score.
Timeline
- 3 Aug 2026, 14:16 UTC Published by the maintainers as a GitHub repository advisory
- 31 Oct 2026, 14:24 UTC First seen by agentprime
- 31 Oct 2026, 14:24 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-g2gp-3wwq-f4ph
- OSV: GHSA-g2gp-3wwq-f4ph
- github.com/thephpleague/commonmark/security/advisories/GHSA-g2gp-3wwq-f4ph
- github.com/thephpleague/commonmark/commit/2d4c0fafa62501be919262064cffa6d71687430b
- github.com/thephpleague/commonmark
- github.com/thephpleague/commonmark/releases/tag/2.9.0