CVE-2026-87946 in SAML SSO
Summary
by MITRE • 10/22/2026
Observable Timing Discrepancy vulnerability in Drupal SAML SSO - Service Provider allows Brute Force. This issue affects SAML SSO - Service Provider versions: from 0.0.0 to 3.2.0.
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Analysis
by VulDB Data Team • 10/22/2026
The identified security flaw represents a classic observable timing discrepancy within the Drupal SAML Single Sign-On Service Provider module, specifically affecting version ranges from 0.0.0 through 3.2.0. This vulnerability stems from an implementation error in how the authentication subsystem processes incoming assertions and validates user credentials against the local database or identity store. In secure cryptographic implementations and robust access control mechanisms, operations such as password hashing verification should execute with constant time complexity to prevent attackers from deducing valid inputs based on response latency. However, in this specific module version, the validation logic likely performs early exits or sequential checks that do not mask the duration of processing for invalid versus valid credentials. This lack of timing uniformity creates a side-channel attack vector where an adversary can measure the time taken by the server to respond to authentication requests and use these measurements to infer whether a provided username exists in the system or if specific password characters are correct.
From a technical perspective, this flaw aligns with CWE-208, which defines Observable Timing Discrepancy as a vulnerability where an attacker can determine information about internal state by measuring response times. The operational impact is severe because it effectively neutralizes the security benefits of strong password policies for accounts targeted via this vector. An attacker does not need to guess passwords blindly through traditional brute force attempts that trigger account lockouts or rate limiting thresholds based on failed login counts alone. Instead, they can employ a more sophisticated timing-based attack where each character of a potential password is guessed by observing minute differences in server response times. This allows for the systematic reconstruction of valid credentials with significantly fewer requests than conventional dictionary attacks, thereby bypassing standard brute force protections that rely solely on request frequency monitoring rather than content analysis or constant-time execution guarantees.
This vulnerability also maps to MITRE ATT&CK technique T1110.004, which describes Password Spraying using timing side-channels, although it is more broadly applicable to credential guessing via timing attacks under the general category of brute force techniques enhanced by environmental feedback. The ability to distinguish between valid and invalid usernames or partial password matches allows an attacker to perform targeted account enumeration followed by precise credential recovery. This compromises the confidentiality and integrity of user accounts associated with the Drupal site, potentially leading to unauthorized access to sensitive content, privilege escalation if administrative roles are compromised, and further exploitation of downstream systems that trust the SAML assertions issued after successful authentication.
Mitigation strategies must address both the immediate code defect and broader architectural security postures. The primary remediation is a mandatory upgrade to version 3.2.1 or later of the Drupal SAML SSO - Service Provider module, where developers have implemented constant-time comparison algorithms for credential validation steps. This ensures that processing time remains consistent regardless of whether input matches stored hashes partially or fully. Additionally, administrators should enforce multi-factor authentication (MFA) to add a layer of security independent of password strength and timing characteristics. Implementing robust rate limiting based on IP address and user agent combinations can also help mitigate the volume of requests an attacker can send in a given timeframe, although this is secondary to fixing the underlying code flaw. Regular security audits focusing on authentication flows and adherence to OWASP guidelines for session management and input validation are recommended to prevent similar side-channel vulnerabilities from being introduced or overlooked in future updates.