CVE-2017-12868 in SimpleSAMLphp
Summary
by MITRE
The secureCompare method in lib/SimpleSAML/Utils/Crypto.php in SimpleSAMLphp 1.14.13 and earlier, when used with PHP before 5.6, allows attackers to conduct session fixation attacks or possibly bypass authentication by leveraging missing character conversions before an XOR operation.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 12/27/2022
The vulnerability identified as CVE-2017-12868 resides within the SimpleSAMLphp authentication framework, specifically in the secureCompare method located in lib/SimpleSAML/Utils/Crypto.php. This flaw affects versions 1.14.13 and earlier, creating a significant security risk when the software operates with PHP versions prior to 5.6. The vulnerability stems from improper handling of character conversions during cryptographic operations, specifically before XOR operations are performed. The issue manifests when attackers can manipulate the comparison process to bypass authentication mechanisms or establish session fixation attacks, undermining the fundamental security guarantees that authentication systems should provide.
The technical implementation of this vulnerability exploits a weakness in the cryptographic comparison function that is designed to prevent timing attacks by performing constant-time string comparisons. However, when operating with PHP versions before 5.6, the secureCompare method fails to properly normalize character encodings before executing XOR operations. This incomplete character conversion process creates a timing differential that attackers can measure and exploit to determine the correct authentication credentials or session identifiers. The flaw represents a classic example of a timing attack vector where the execution time of the comparison function varies based on the input values, allowing attackers to gradually deduce the correct values through statistical analysis. This vulnerability directly maps to CWE-203, which describes the exposure of information through timing differences, and aligns with ATT&CK technique T1212 for exploitation of information disclosure vulnerabilities.
The operational impact of this vulnerability extends beyond simple authentication bypasses to encompass broader session management compromises. Attackers can leverage this weakness to conduct session fixation attacks by manipulating session tokens during the authentication process, potentially allowing them to hijack user sessions or impersonate legitimate users. The vulnerability's scope increases when considering that SimpleSAMLphp is commonly deployed in enterprise environments for single sign-on solutions, making the potential impact substantial for organizations relying on these authentication frameworks. The timing characteristics of the flaw make it particularly dangerous because it can be exploited through automated tools, requiring minimal expertise from attackers while potentially providing complete access to protected systems. Organizations using vulnerable versions face risks including unauthorized access to sensitive data, privilege escalation, and potential lateral movement within their networks through compromised authentication systems.
Mitigation strategies for CVE-2017-12868 primarily involve upgrading to SimpleSAMLphp versions that address this vulnerability, specifically versions 1.14.14 and later. Additionally, organizations should ensure they are running PHP 5.6 or later, as the vulnerability specifically affects systems with older PHP versions where the character conversion handling is insufficient. Security teams should implement monitoring for unusual authentication patterns that might indicate exploitation attempts, particularly focusing on timing variations in authentication responses. The recommended approach includes comprehensive patch management procedures to ensure all instances of SimpleSAMLphp are updated, along with verification that the underlying PHP environment meets the minimum version requirements. Network segmentation and additional authentication layers can provide defense-in-depth measures while patches are being deployed, though these are temporary mitigations rather than permanent solutions to the core vulnerability. Organizations should also conduct thorough security assessments of their authentication infrastructure to identify any other systems that might be similarly vulnerable to timing attacks or improper cryptographic implementation.