TI-2026-22160 Aliases CVE-2026-27807

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

LOW 22CWE-776Published 2026-03-06 · Updated 2026-03-06

Key facts

Attack vector: Network
Privileges required: High
User interaction: None
Attack complexity: Low
Impact type: —
Confidentiality · integrity · availability: None · None · High
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00323 25th percentileScored 2026-11-07

Fix Fixed Markus (MarkUsProject): 2.9.4

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
MarkUsProject	Markus	before 2.9.4	2.9.4	Patch available	CNA

Markus VendorMarkUsProject Affected before 2.9.4 Fixed in 2.9.4 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:markusproject:markus::::::::	before 2.9.4	Vulnerable	MarkUsProject

cpe:2.3:a:markusproject:markus:*:*:*:*:*:*:*:* Versions before 2.9.4 Vulnerable ·MarkUsProject

Remediation

Fix · CNA Markus (MarkUsProject) Fixed in 2.9.4

Timeline

2026-10-02 Threatist record created from CVE-2026-27807

References

Advisory 1

https://github.com/MarkUsProject/Markus/security/advisories/GHSA-m9rx-85mx-q9h6

Other 1

https://github.com/MarkUsProject/Markus/releases/tag/v2.9.4

TI-2026-20241 Zip Slip in MarkUs config upload allowing RCE CVSS 3.1CRITICAL 9.1
TI-2026-22679 MarkUs: Stored XSS in Submission HTML Preview Enables Instructor-Context Actions CVSS 3.1HIGH 8.0
TI-2024-34648 Arbitrary File Write leading up to remote code execution (instructor accounts) CVSS 4.0HIGH 7.1
TI-2024-34420 MarkUs Arbitrary File Write leading up to remote code execution (student accounts) CVSS 4.0HIGH 7.1
TI-2026-20987 MarkUs: Zip bomb in config upload enables DoS CVSS 3.1MEDIUM 6.5
TI-2026-20085 MarkUs has a submission-view IDOR exposes all student submissions CVSS 3.1MEDIUM 6.5

See all 7 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences