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.

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 file…

EPSS: 0.001 (21.8th percentile) — read the EPSS interpretation.

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.

Affected products

Markusproject Markus — versions < 2.9.4

Weakness classification (CWE)

CWE-776 — Improper Restriction of Recursive Entity References in DTDs (XML Entity Expansion)

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)

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.