CVE-2019-18887 in Symfony
Summary
by MITRE
An issue was discovered in Symfony 2.8.0 through 2.8.50, 3.4.0 through 3.4.34, 4.2.0 through 4.2.11, and 4.3.0 through 4.3.7. The UriSigner was subject to timing attacks. This is related to symfony/http-kernel.
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Analysis
by VulDB Data Team • 02/26/2024
The vulnerability CVE-2019-18887 affects the Symfony framework, specifically impacting versions from 2.8.0 through 2.8.50, 3.4.0 through 3.4.34, 4.2.0 through 4.2.11, and 4.3.0 through 4.3.7. This security flaw resides within the UriSigner component which is part of the symfony/http-kernel package, making it a critical concern for applications relying on Symfony's URL signing functionality. The issue stems from the implementation of cryptographic operations that do not properly handle timing variations, creating potential attack vectors for adversaries seeking to exploit temporal inconsistencies in the verification process.
The technical flaw manifests as a timing attack vulnerability in the UriSigner's verification mechanism, where the comparison operation between expected and actual signatures does not execute in constant time. This timing inconsistency allows attackers to measure response times during signature verification and infer information about the correct signature through statistical analysis. The vulnerability is classified under CWE-330 as the use of insecure cryptographic algorithms or improper implementation of cryptographic functions, specifically focusing on the lack of constant-time comparison in cryptographic operations. The attack pattern aligns with techniques described in the MITRE ATT&CK framework under T1212 as "Exploitation for Credential Access" where adversaries leverage timing variations to extract cryptographic secrets.
The operational impact of this vulnerability extends across multiple Symfony versions and affects applications that utilize URL signing for security purposes such as password reset links, session management, or API access tokens. Attackers could potentially reconstruct valid signatures through repeated timing measurements, leading to unauthorized access to protected resources. The implications are particularly severe for applications handling sensitive user data or administrative functions, as successful exploitation could result in privilege escalation or data compromise. Organizations using affected Symfony versions face significant risk when implementing security mechanisms that depend on URI signing for access control and authentication purposes.
Mitigation strategies for CVE-2019-18887 include immediate upgrade to patched versions of Symfony, specifically versions 2.8.51, 3.4.35, 4.2.12, and 4.3.8 which contain the necessary fixes. Organizations should also implement constant-time comparison algorithms in their cryptographic implementations and consider additional security measures such as rate limiting and monitoring for suspicious timing patterns. The fix addresses the root cause by ensuring that signature verification operations execute in constant time regardless of input values, preventing timing variations that could be exploited by attackers. Security teams should conduct comprehensive testing of applications after applying patches to ensure no regressions in functionality while maintaining the enhanced security posture. Additionally, organizations should review their overall cryptographic implementation practices to prevent similar timing attack vulnerabilities in other components of their software stack.