CVE-2026-27807
Markusproject Markus ≤ 2.9.4
Raw vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:HSummary
CVE-2026-27807 is a medium-severity XML Entity Expansion (CWE-776) vulnerability in Markusproject Markus. Its CVSS base score is 4.9 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Endpoint Denial of Service (T1499); ranked at the 21th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to CM-6 (Configuration Settings) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-9968
Vulnerability Data
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.…
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This issue has been patched in version 2.9.4.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Secure configuration settings can disable DTD processing or cap entity expansion in XML parsers.
Input validation can enforce limits on XML entity expansion and recursion depth before parsing occurs.
Least-functionality configuration can prohibit unsafe DTD features or external entity resolution.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly prevent introduction of improper recursive entity handling in XML code.
Hardened configuration baselines can disable or limit DTD entity expansion in XML parsers.
Identifying and recording vulnerabilities can discover XML entity expansion flaws before exploitation.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can detect and block XML entity-expansion vulnerabilities before deployment.
Secure SDLC mandates input validation and parser hardening that can prevent unbounded entity expansion.
Application security requirements can explicitly call for limits on XML entity recursion and DTD processing.
Secure architecture principles discourage unsafe parser configurations that enable entity expansion attacks.
Secure coding standards directly require disabling or restricting recursive entity references in XML parsers.