CVE-2024-50343 in Symfony
Summary
by MITRE • 11/06/2024
symfony/validator is a module for the Symphony PHP framework which provides tools to validate values. It is possible to trick a `Validator` configured with a regular expression using the `$` metacharacters, with an input ending with `\n`. Symfony as of versions 5.4.43, 6.4.11, and 7.1.4 now uses the `D` regex modifier to match the entire input. Users are advised to upgrade. There are no known workarounds for this vulnerability.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 11/12/2024
The vulnerability identified as CVE-2024-50343 affects the symfony/validator module within the Symfony PHP framework, specifically targeting regular expression validation mechanisms that utilize the `$` metacharacter. This flaw represents a classic input validation bypass issue where attackers can manipulate validation logic through carefully crafted input sequences. The vulnerability stems from how the validator processes regular expressions that include the end-of-string anchor metacharacter, creating potential security gaps in applications that rely on Symfony's validation capabilities for data sanitization and input verification.
The technical implementation of this vulnerability involves the interaction between PHP's regular expression engine and Symfony's validation framework when processing inputs that end with newline characters. The `$` metacharacter in regular expressions typically matches the end of a string, but when combined with certain input patterns ending in newline characters, it can be circumvented through specific regex matching behaviors. This occurs because the original validation logic did not properly account for the distinction between the end of string and end of line boundaries, allowing malicious inputs to bypass validation checks that should have rejected them based on the specified regular expression patterns.
The operational impact of this vulnerability extends beyond simple validation bypass scenarios to potentially compromise application security controls that depend on proper input validation. Attackers could exploit this weakness to submit malicious data that passes validation checks, potentially leading to injection attacks, data corruption, or unauthorized access to application resources. The vulnerability affects multiple Symfony versions including 5.4.43, 6.4.11, and 7.1.4, indicating it's a widespread issue across the framework's current release lines. This affects organizations that use Symfony's validation components for user input processing, form validation, and data integrity checks, potentially exposing their applications to various attack vectors that rely on bypassing security controls.
Security researchers categorize this vulnerability under CWE-20: Improper Input Validation, which addresses weaknesses in input validation that can lead to various security issues. The ATT&CK framework would classify this as a technique involving input validation bypass, potentially enabling other attack phases such as command injection, data manipulation, or privilege escalation depending on the application context. The lack of known workarounds means organizations must rely entirely on upgrading their Symfony framework installations to receive the patched behavior that incorporates the `D` regex modifier. This modifier ensures that the `$` metacharacter matches only the end of the string and not the end of line, effectively closing the validation bypass window.
Organizations should prioritize immediate upgrade of their Symfony installations to versions 5.4.43, 6.4.11, or 7.1.4 where the `D` regex modifier has been implemented to address this vulnerability. The fix demonstrates proper security engineering practices by addressing the root cause rather than implementing temporary workarounds. Security teams should conduct comprehensive testing of their applications after applying the upgrade to ensure no regressions in existing validation logic while confirming that the vulnerability has been properly resolved. The vulnerability highlights the importance of proper regex handling in security-critical components and reinforces the need for regular security updates and vulnerability management processes within development environments.