CVE-2026-93582 in OTRS Community Edition
Summary
by MITRE • 10/12/2026
The 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
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Analysis
by VulDB Data Team • 10/13/2026
The vulnerability identified in OTRS Community Edition versions 6 and prior represents a critical authentication bypass flaw rooted in improper handling of HTTP request headers within CGI and mod_perl deployment environments. This issue, classified under CWE-287 as an Improper Authentication mechanism, allows unauthenticated remote attackers to impersonate legitimate users by manipulating the REMOTE_USER or HTTP_REMOTE_USER environment variables. In standard web server configurations such as Apache with mod_cgi or mod_perl, incoming HTTP headers are often automatically mapped into corresponding CGI environment variables prefixed with HTTP_. Consequently, a malicious actor can inject a crafted Remote-User header into their request, which the underlying web server translates and exposes to the OTRS application via the HTTP_REMOTE_USER variable.
The core technical flaw lies in how the OTRS authentication module processes these inputs when Basic Authentication is configured as the backend. The system exhibits excessive trust in external environment variables without performing sufficient validation or password verification. Specifically, if the HTTP_REMOTE_USER variable is populated by an attacker-controlled header, the application accepts this value as a pre-authenticated username identity. This bypasses the standard credential exchange process where a valid password must be verified against stored hashes. As a result, the authentication logic fails to distinguish between a legitimately authenticated session and one forged through environment variable manipulation, effectively granting access based solely on the presence of the header rather than proof of possession of secret credentials.
The operational impact of this vulnerability is severe, as it enables complete identity spoofing for any existing agent or customer user within the OTRS system. An attacker who successfully exploits this flaw gains full privileges associated with the impersonated account. Depending on the role and permissions of the targeted user, this can lead to unauthorized access to sensitive ticket data, confidential business information, and personal details stored in the helpdesk database. Furthermore, if the compromised account possesses administrative rights or specific configuration modification capabilities, the attacker could alter system settings, inject malicious scripts into workflows, or exfiltrate large volumes of structured data. This directly compromises the confidentiality, integrity, and availability principles central to cybersecurity frameworks like NIST SP 800-53.
From a threat intelligence perspective, this attack vector aligns with MITRE ATT&CK technique T1078, specifically Valid Accounts, where adversaries use legitimate credentials or identities to bypass authentication controls. The exploitation requires specific environmental conditions: the target must be running OTRS Community Edition 6.x or earlier, configured with HTTP Basic Authentication as a backend, and hosted on a web server that exposes arbitrary headers via environment variables. This limits the attack surface but does not mitigate the severity for affected deployments. Organizations relying on legacy versions of OTRS in traditional CGI environments are at significant risk unless immediate remediation steps are taken to restrict header exposure or disable vulnerable authentication methods.
Mitigation strategies focus on eliminating the trust boundary violation and upgrading infrastructure components. The most effective long-term solution is to upgrade to OTRS version 7 or later, which utilizes the Mojolicious/Hypnotoad framework that does not expose arbitrary request headers through environment variables in a manner exploitable by this vector. Additionally, newer versions enforce validation of the REMOTE_USER mechanism through configured SSO shared secrets and have removed the insecure HTTP_REMOTE_USER fallback entirely as a security hardening measure. For systems unable to upgrade immediately, administrators should configure their web servers to strip or ignore Remote-User headers before they reach the application layer. Alternatively, switching authentication backends away from Basic Authentication to more secure methods such as SAML, LDAP with proper binding, or OAuth can prevent this specific bypass path while maintaining access control integrity.