CVE-2021-28834
Kramdown before 2.3.1 does not restrict Rouge formatters to the Rouge::Formatters namespace, and thus arbitrary classes can be instantiated.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (2.70%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
Kramdown before 2.3.1 does not restrict Rouge formatters to the Rouge::Formatters namespace, and thus arbitrary classes can be instantiated.
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 2.70% probability · 86th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Affected
- kramdown project/kramdown · fedoraproject/fedora · debian/debian linux
- Source
- cve@mitre.org
EPSS 2.7% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://github.com/gettalong/kramdown/compare/REL_2_3_0...REL_2_3_1Patch, Third Party Advisory
- https://github.com/gettalong/kramdown/pull/708Exploit, Third Party Advisory
- https://gitlab.com/gitlab-org/gitlab/-/commit/179329b5c3c118924fb242dc449d06b4ed6ccb66Patch, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NJCJVYHPY6LNUFM6LYZIAUIYOMVT5QGV/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/S3BBLUIDCUUR3NEE4NJLOCCAV3ALQ3O6/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SYOLQKFL6IJCQLBXV34Z4TI4O54GESPR/
- https://www.debian.org/security/2021/dsa-4890Third Party Advisory
- https://github.com/gettalong/kramdown/compare/REL_2_3_0...REL_2_3_1Patch, Third Party Advisory
- https://github.com/gettalong/kramdown/pull/708Exploit, Third Party Advisory
- https://gitlab.com/gitlab-org/gitlab/-/commit/179329b5c3c118924fb242dc449d06b4ed6ccb66Patch, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NJCJVYHPY6LNUFM6LYZIAUIYOMVT5QGV/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/S3BBLUIDCUUR3NEE4NJLOCCAV3ALQ3O6/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/SYOLQKFL6IJCQLBXV34Z4TI4O54GESPR/
- https://www.debian.org/security/2021/dsa-4890Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.