CVE-2024-28859 in symfony1
Summary
by MITRE • 03/16/2024
Symfony1 is a community fork of symfony 1.4 with DIC, form enhancements, latest Swiftmailer, better performance, composer compatible and PHP 8 support. Symfony 1 has a gadget chain due to vulnerable Swift Mailer dependency that would enable an attacker to get remote code execution if a developer unserialize user input in his project. This vulnerability present no direct threat but is a vector that will enable remote code execution if a developper deserialize user untrusted data. Symfony 1 depends on Swift Mailer which is bundled by default in vendor directory in the default installation since 1.3.0. Swift Mailer classes implement some `__destruct()` methods. These methods are called when php destroys the object in memory. However, it is possible to include any object type in `$this->_keys` to make PHP access to another array/object properties than intended by the developer. In particular, it is possible to abuse the array access which is triggered on foreach($this->_keys ...) for any class implementing ArrayAccess interface. This may allow an attacker to execute any PHP command which leads to remote code execution. This issue has been addressed in version 1.5.18. Users are advised to upgrade. There are no known workarounds for this vulnerability.
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Analysis
by VulDB Data Team • 12/05/2025
The vulnerability described in CVE-2024-28859 represents a critical remote code execution risk within Symfony 1 applications that utilize the Swift Mailer dependency. This issue stems from a deserialization flaw in the Swift Mailer component that has been integrated into Symfony 1 since version 1.3.0, making it a persistent threat across multiple versions of the framework. The vulnerability operates through a gadget chain mechanism where untrusted data deserialization leads to arbitrary code execution, fundamentally compromising application security and potentially enabling full system compromise. The attack vector is particularly dangerous because it leverages legitimate PHP object destruction mechanisms, making it difficult to detect and prevent through standard security measures.
The technical flaw manifests in Swift Mailer's implementation of `__destruct()` methods that process `$this->_keys` array during object cleanup. When developers inadvertently unserialize user-provided input, attackers can manipulate the deserialization process to inject malicious objects that exploit the ArrayAccess interface implementation. This creates a chain reaction where PHP's foreach loop on `$this->_keys` triggers unintended object property access, allowing attackers to execute arbitrary PHP commands through carefully crafted serialized data. The vulnerability specifically targets the interaction between PHP's object destruction lifecycle and the Swift Mailer's internal array handling, creating an exploitable path that bypasses normal input validation mechanisms. This type of vulnerability is classified as a deserialization vulnerability under CWE-502, specifically involving unsafe deserialization of untrusted data.
The operational impact of this vulnerability extends far beyond simple data compromise, as it provides attackers with complete remote code execution capabilities within the application environment. Once exploited, attackers can execute arbitrary commands, potentially gaining access to sensitive data, escalating privileges, or using the compromised system as a pivot point for further attacks within the network. The vulnerability affects any Symfony 1 application that handles user input through deserialization processes, making it particularly dangerous for web applications that process email or user-generated content. The fact that Swift Mailer is bundled by default in Symfony 1 installations since version 1.3.0 means that a significant number of applications are potentially vulnerable, creating a widespread security concern. This vulnerability aligns with ATT&CK technique T1059.007 for command and script injection, enabling attackers to execute malicious code through the application's legitimate email processing functionality.
The remediation strategy focuses entirely on upgrading to Symfony 1.5.18 or later versions where the vulnerability has been patched. The fix addresses the underlying deserialization issue in Swift Mailer's object destruction handling, specifically by properly validating and sanitizing the data within the `_keys` array before processing. Organizations must ensure that all Symfony 1 applications are updated immediately, as no workarounds exist for this vulnerability. The patch implementation involves modifying the object destruction logic to prevent unauthorized access to array properties and ensuring that only expected object types are processed during cleanup operations. Security teams should conduct comprehensive vulnerability assessments across all Symfony 1 installations to identify and remediate affected systems, as the vulnerability's exploitation potential makes immediate action critical for maintaining application security posture. This vulnerability demonstrates the importance of keeping dependencies updated and the risks associated with legacy frameworks that may contain unpatched security flaws.