CVE-2026-18259 in Token Content Access
Summary
by MITRE • 08/26/2026
Observable Timing Discrepancy vulnerability in Drupal Token Content Access allows Brute Force. This issue affects Token Content Access versions: from 0.0.0 to 3.1.2.
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Analysis
by VulDB Data Team • 08/26/2026
The observed timing discrepancy within the Drupal module known as Token Content Access, specifically affecting versions ranging from 0.0.0 through 3.1.2, represents a classic side-channel vulnerability that undermines the integrity of access control mechanisms by leaking information about authentication states or token validity through response latency variations. This flaw arises because the application processes valid tokens and invalid tokens with different computational costs or execution paths, resulting in measurable differences in server response times. An attacker can exploit this inconsistency to perform timing-based brute force attacks against user credentials or session tokens without triggering traditional rate-limiting mechanisms that are often designed to detect high-frequency request patterns rather than subtle temporal anomalies. The vulnerability is rooted in the failure of the module to implement constant-time comparison algorithms when validating access tokens, a fundamental requirement for secure cryptographic operations and authentication checks as outlined by industry standards such as CWE-208 which classifies this behavior under observable timing differences that can lead to information disclosure.
From an operational perspective, this vulnerability allows malicious actors to systematically deduce valid user identifiers or session keys by analyzing the time taken for the server to respond to various input combinations. By sending a high volume of requests with slight variations in the token payload and measuring the precise response duration using automated scripts, an attacker can statistically determine which inputs result in faster processing times, thereby narrowing down the correct credentials over successive iterations. This method is particularly dangerous because it operates below the threshold of most intrusion detection systems that monitor for volumetric attacks or obvious error spikes. The impact extends beyond simple unauthorized access; it compromises the confidentiality and integrity of user accounts associated with protected content within Drupal sites utilizing this module, potentially leading to data exfiltration, privilege escalation, or further exploitation of other vulnerabilities once initial foothold is established.
The technical root cause lies in the implementation details of how the Token Content Access module handles token verification logic during HTTP requests. When a request contains an invalid token, the system may fail early in the validation chain due to format errors or immediate rejection checks, whereas valid tokens might proceed through additional database lookups, permission evaluations, or cryptographic verifications that consume more processing time. This asymmetry creates a distinguishable signal for attackers who can measure latency with millisecond precision using tools like Burp Suite Intruder custom headers or specialized timing attack frameworks. To mitigate this risk, developers must ensure that all token comparisons are performed in constant time, meaning the execution duration remains identical regardless of whether the input is correct or incorrect up to the final byte comparison. This typically involves implementing a secure string comparison function such as hash_equals in PHP environments where Drupal operates, ensuring that partial matches do not result in early exits from the validation routine.
Furthermore, defense-in-depth strategies should be employed to counteract residual risks even after code remediation. Implementing strict rate limiting based on IP address and user agent combinations can disrupt automated timing attacks by introducing artificial delays or blocking requests after a certain threshold is exceeded. Additionally, enabling comprehensive logging of authentication failures and monitoring for statistical anomalies in request latency patterns can aid in early detection of such attempts. Organizations should also consider upgrading to the latest patched versions of Drupal modules where this issue has been resolved, ensuring that security patches are applied promptly upon release. Adherence to secure coding guidelines referenced by OWASP Top Ten categories related to Broken Access Control and Cryptographic Failures is essential for maintaining robust security postures against sophisticated timing-based exploitation techniques.