CVE-2011-0910 in Forums
Summary
by MITRE
The cookie implementation in Vanilla Forums before 2.0.17.6 makes it easier for remote attackers to spoof signed requests, and consequently obtain access to arbitrary user accounts, via HMAC timing attacks.
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Analysis
by VulDB Data Team • 02/08/2019
The vulnerability identified as CVE-2011-0910 resides within the cookie implementation of Vanilla Forums software prior to version 2.0.17.6, representing a critical security flaw that enables remote attackers to exploit HMAC timing attacks for account impersonation. This vulnerability specifically targets the cryptographic signing mechanism used to validate cookie integrity, creating a pathway for malicious actors to forge authenticated requests and gain unauthorized access to user accounts. The flaw stems from insufficient protection against timing attacks that can be leveraged to determine the validity of HMAC signatures through measurable differences in processing time.
The technical implementation of this vulnerability involves the use of HMAC (Hash-based Message Authentication Code) for cookie validation within the Vanilla Forums platform. When a user authenticates, the system generates a signed cookie containing user session information. However, the implementation lacks proper constant-time comparison functions when validating HMAC signatures. This timing variation allows attackers to perform side-channel analysis by measuring the time differences between valid and invalid HMAC validations, ultimately enabling them to reconstruct valid signatures for arbitrary user accounts without requiring legitimate credentials. The vulnerability directly maps to CWE-320, which addresses weaknesses in the generation or use of cryptographic keys, and more specifically to CWE-328, which deals with the use of weak hash functions or improper hash usage that can be exploited through timing attacks.
From an operational perspective, this vulnerability presents a severe risk to organizations utilizing Vanilla Forums for community management, customer support, or internal collaboration platforms. Attackers can exploit this weakness to impersonate any user account within the system, potentially gaining access to sensitive personal information, private communications, and administrative privileges. The attack vector requires only remote access to the vulnerable system, making it particularly dangerous as it can be executed from anywhere on the internet without requiring physical access or privileged network positions. The implications extend beyond simple unauthorized access, as compromised accounts can be used to post malicious content, alter forum configurations, or conduct further attacks on the broader network infrastructure.
The mitigation strategy for this vulnerability requires immediate implementation of a patched version of Vanilla Forums, specifically version 2.0.17.6 or later, which addresses the timing attack susceptibility through proper constant-time cryptographic comparisons. Organizations should also implement additional security measures including monitoring for unusual authentication patterns, enforcing strong password policies, and implementing multi-factor authentication where possible. Network-level protections such as intrusion detection systems and web application firewalls can help detect anomalous traffic patterns associated with timing attack attempts. The remediation process should also include comprehensive security testing to ensure that no other cryptographic implementations within the platform suffer from similar timing vulnerabilities, following best practices outlined in NIST SP 800-131A for cryptographic algorithm migration and security requirements. This vulnerability highlights the importance of implementing proper cryptographic practices that resist side-channel attacks, particularly in web applications where timing variations can be exploited to compromise security mechanisms.