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CVE-2021-28834Kramdown before 2.3.1 does not restrict Rouge formatters to the Rouge::Formatters namespace, and thus arbitrary classes can be instantiated.
- 9.8CriticalCVSS base score
- 2.7%Exploitation in 30 daysEPSS · top 14% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
Kramdown before 2.3.1 does not restrict Rouge formatters to the Rouge::Formatters namespace, and thus arbitrary classes can be instantiated.
Timeline
ID reserved
By mitre
Published
- 3 years later
· 3 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.1 | Critical9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 2.7% · top 14% of all CVEs (13 Nov 2026)
Loading the EPSS history…
The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.8.
Affected products
n/a
- affected n/a
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- RubyGemskramdownGHSA-52p9-v744-mwjj (opens in a new tab)
References
References7
- https://github.com/gettalong/kramdown/pull/708 (opens in a new tab)x_refsource_MISCx_transferred
- https://gitlab.com/gitlab-org/gitlab/-/commit/179329b5c3c118924fb242dc449d06b4ed6ccb66 (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/gettalong/kramdown/compare/REL_2_3_0...REL_2_3_1 (opens in a new tab)x_refsource_MISCx_transferred
- FEDORA-2021-139a6a2f9d (opens in a new tab)vendor-advisoryx_refsource_FEDORAx_transferred
- FEDORA-2021-4c57a892d1 (opens in a new tab)vendor-advisoryx_refsource_FEDORAx_transferred
- FEDORA-2021-edc673e864 (opens in a new tab)vendor-advisoryx_refsource_FEDORAx_transferred
- DSA-4890 (opens in a new tab)vendor-advisoryx_refsource_DEBIANx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2021-0603 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-52p9-v744-mwjj (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2021-28834)Record last updated .