CVE-2026-27807CWE-776

MarkUs: YAML alias (‘billion laughs’) DoS in config upload

Medium · published March 6, 2026

CVSS v3.1
4.9
EPSS
0%
Percentile
40.8
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
4.9 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
CVSS v4.0
Not supplied
EPSS
0.00485 · 40.8th percentile
Weakness
CWE-776 · Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
Published
2026-03-06T02:48Z
EPSS history
Timeline
  • 06 MAR 02:48Z
    MarkUs: YAML alias (‘billion laughs’) DoS in config upload
    cvelistv5