CVE-2026-63177

Malcolm Vulnerable to Authorization Bypass via URI Normalization Differential in Nginx Lua RBAC

Published Aug 11, 2026 CVSS 4.0 · 7.1 High EPSS < 1% KEV · Not listed
Description
Malcolm is a network traffic analysis tool suite. Prior to version 26.07.0, role-based access control enforced in the Nginx OpenResty Lua layer evaluates the raw, unnormalized `ngx.var.request_uri`, while Nginx itself routes requests using the normalized path. An authenticated low-privilege user can prepend a traversal segment (for example `/x/../upload/...`) so that Nginx routes the request to a restricted backend while the Lua role check fails to match any rule and falls open, granting access it should deny. Version 26.07.0 fixes the issue.

Remediation

Vendor Solution

Malcolm version 26.07.0 addresses these issues. For more information, see  https://github.com/cisagov/Malcolm/pull/1043

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
References
Metrics cvssV4_0

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

Type Values Removed Values Added
First Time appeared Cisagov
Cisagov malcolm
Vendors & Products Cisagov
Cisagov malcolm
Type Values Removed Values Added
Metrics ssvc

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

Type Values Removed Values Added
Description Malcolm is a network traffic analysis tool suite. Prior to version 26.07.0, role-based access control enforced in the Nginx OpenResty Lua layer evaluates the raw, unnormalized `ngx.var.request_uri`, while Nginx itself routes requests using the normalized path. An authenticated low-privilege user can prepend a traversal segment (for example `/x/../upload/...`) so that Nginx routes the request to a restricted backend while the Lua role check fails to match any rule and falls open, granting access it should deny. Version 26.07.0 fixes the issue.
Title Malcolm Vulnerable to Authorization Bypass via URI Normalization Differential in Nginx Lua RBAC
Weaknesses CWE-863
References
Metrics cvssV3_1

{'score': 7.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Oct 2, 2026, 8:27 PM
Reserved
Jul 15, 2026, 10:13 PM
Status
Awaiting Analysis
Published
Aug 11, 2026, 9:17 PM
Modified
Oct 24, 2026, 4:10 PM