CVE-2026-90447

Authentication Bypass by Spoofing in Malcolm

Published Sep 11, 2026 CVSS 4.0 · 7.1 High EPSS < 1% KEV · Not listed
Description
A routing rule selects between two different authentication mechanisms for the same downstream service based on the value of a client-supplied request header, rather than on any property the client cannot control. An authenticated user in possession of a shared service credential can set this header to route around the primary role-based authorization check and reach the alternate path's fixed, elevated role instead. This allows a low-privileged authenticated attacker who knows the shared credential to perform actions reserved for a higher-privileged role.

Remediation

Vendor Solution

The latest version of Malcolm (September 2026 or later) fixes these vulnerabilities. Affected users are encouraged to update their instance of Malcolm to the latest version.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Title Authentication Bypass by Spoofing in Malcolm
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N'}

Type Values Removed Values Added
Title Header-Based Authentication Bypass Grants Elevated Role
Type Values Removed Values Added
Title Header-Based Authentication Bypass Grants Elevated Role
Type Values Removed Values Added
Title Header‑based routing permits privilege escalation by circumventing role‑based authorization
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Title Header‑based routing permits privilege escalation by circumventing role‑based authorization
Type Values Removed Values Added
Title Privilege Escalation via Header‑Based Authentication Bypass in Malcolm
Type Values Removed Values Added
First Time appeared Cisagov
Cisagov malcolm
Vendors & Products Cisagov
Cisagov malcolm
Type Values Removed Values Added
Title Privilege Escalation via Header‑Based Authentication Bypass in Malcolm
Type Values Removed Values Added
Title Client‑Supplied Header Bypasses Role‑Based Authorization in Malcolm
Type Values Removed Values Added
Title Client‑Supplied Header Bypasses Role‑Based Authorization in Malcolm
Type Values Removed Values Added
Title Routing Header Manipulation Allows Privilege Escalation in Malcolm
Type Values Removed Values Added
Title Routing Header Manipulation Allows Privilege Escalation in Malcolm
Type Values Removed Values Added
Description A routing rule selects between two different authentication mechanisms for the same downstream service based on the value of a client-supplied request header, rather than on any property the client cannot control. An authenticated user in possession of a shared service credential can set this header to route around the primary role-based authorization check and reach the alternate path's fixed, elevated role instead. This allows a low-privileged authenticated attacker who knows the shared credential to perform actions reserved for a higher-privileged role.
Weaknesses CWE-290
References
Metrics cvssV4_0

{'score': 7.1, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
icscert
Published
Updated
Oct 2, 2026, 9:12 PM
Reserved
Sep 11, 2026, 9:00 PM
Status
Awaiting Analysis
Published
Sep 11, 2026, 10:16 PM
Modified
Oct 2, 2026, 10:16 PM