Vulnerability · Published Mar 6, 2026 · Assigned by GitHub_M
CVE-2026-27807MarkUs: YAML alias (‘billion laughs’) DoS in config upload
Medium 4.9
In plain English
A medium-severity security flaw in Markus from MarkUsProject. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 25% of all known vulnerabilities).
Severity (CVSS 3.1)4.9Medium
Exploit odds (30 days)0.3%top 74.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
MarkUs is a web application for the submission and grading of student assignments. Prior to version 2.9.4, MarkUs allows course instructors to upload YAML files to create/update various entities (e.g., assignment settings). These YAML files are parsed with aliases enabled. This issue has been patched in version 2.9.4.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| MarkUsProject | Markus | < 2.9.4 |
Weakness: CWE-776 · Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
References
- https://github.com/MarkUsProject/Markus/security/advisories/GHSA-m9rx-85mx-q9h6 x_refsource_CONFIRM
- https://github.com/MarkUsProject/Markus/releases/tag/v2.9.4 x_refsource_MISC