XXE in Markusproject Markus
CVE-2026-27807
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.9 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.005 (38.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 38th percentile — 38.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002
Affected products
- Markusproject Markus — versions < 2.9.4
Weakness classification (CWE)
References
- github.com/MarkUsProject/Markus/security/advisories/GHSA-m9rx-85mx-q9h6 (Vendor Advisory)
- github.com/MarkUsProject/Markus/releases/tag/v2.9.4 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-27807?
- CVE-2026-27807 is a medium-severity vulnerability in Markusproject Markus, classified under Improper Restriction of Recursive Entity References in DTDs (XML Entity Expansion). CVSS score: 4.9/10. Published 2026-03-06.
- How severe is CVE-2026-27807?
- Medium severity. CVSS v3 base score is 4.9 out of 10.