Authentication Bypass via Spoofed Remote-User Header in HTTP Basic Authentication

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-93582
StatePUBLISHED
AssignerOTRS
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-12 07:16:37 UTC
Updated2026-10-12 07:16:37 UTC
DescriptionThe HTTP Basic Authentication modules in ((OTRS)) Community Edition 6 and prior accept the authenticated username from either the REMOTE_USER or HTTP_REMOTE_USER environment variable. In CGI and mod_perl based deployments, HTTP request headers may be mapped to corresponding HTTP_* environment variables. As a result, an unauthenticated remote attacker can supply a crafted Remote-User request header which is exposed to the application as HTTP_REMOTE_USER. When HTTP Basic Authentication is configured as the authentication backend, OTRS trusts this value as an already authenticated username and does not perform an additional password verification. An attacker may therefore authenticate through the Generic Interface as an existing agent or customer user without knowing the corresponding credentials. The resulting privileges depend on the account being impersonated. Successful exploitation may allow access to confidential information and modification of data or configuration with the permissions of the affected user. Exploitation requires HTTP Basic Authentication to be configured as an authentication backend and a web server environment in which attacker-controlled HTTP headers are exposed through the corresponding HTTP_* environment variables. OTRS 7 and later are not affected by this attack vector due to the use of Mojolicious/Hypnotoad and does not expose arbitrary request headers through %ENV in the manner required for exploitation. The supported REMOTE_USER mechanism additionally requires validation through the configured SSO shared secret. The unused HTTP_REMOTE_USER fallback has nevertheless been removed as a security-hardening measure. Please note that ((OTRS)) Community Edition 6.x and before are vulnerable. Products based on the ((OTRS)) Community Edition also very likely to be affected

Risk And Classification

Primary CVSS: v3.1 9.4 CRITICAL from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

Problem Types: CWE-290 | CWE-290 CWE-290 Authentication Bypass by Spoofing

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.4CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
3.1CNACVSS9.4CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA OTRS GmbH Former OTRS AG OTRS unaffected 7.0.x Not specified
CNA OTRS GmbH Former OTRS AG OTRS unaffected 8.0.x Not specified
CNA OTRS GmbH Former OTRS AG OTRS unaffected 2023.x Not specified
CNA OTRS GmbH Former OTRS AG OTRS unaffected 2024.x Not specified
CNA OTRS GmbH Former OTRS AG OTRS unaffected 2025.x Not specified
CNA OTRS GmbH Former OTRS AG OTRS unaffected 2026.x Not specified
CNA OTRS GmbH Former OTRS AG OTRS Community Edition affected 6.x Not specified

References

ReferenceSourceLinkTags
otrs.com/release-notes/otrs-security-advisory-2026-18 [email protected] otrs.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Special thanks to Mokrane ABDELMALEK (via Ghent University VDP programme) for finding this vulnerability (en)

Additional Advisory Data

Solutions

CNA: Update to latest version of OTRS (2026.7.1. or later).

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