Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to versions 5.4.51, 6.4.33, 7.3.11, 7.4.5, and 8.0.5, the Symfony Process component did not correctly treat some characters (notably =) as “special” when escaping arguments on Windows. When PHP is executed from an MSYS2-based environment (e.g. Git Bash) and Symfony Process spawns native Windows executables, MSYS2’s argument/path conversion can mis-handle unquoted arguments containing these characters. This can cause the spawned process to receive corrupted/truncated arguments compared to what Symfony intended. If an application (or tooling such as Composer scripts) uses Symfony Process to invoke file-management commands (e.g. rmdir, del, etc.) with a path argument containing =, the MSYS2 conversion layer may alter the argument at runtime. In affected setups this can result in operations being performed on an unintended path, up to and including deletion of the contents of a broader directory or drive. The issue is particularly relevant when untrusted input can influence process arguments (directly or indirectly, e.g. via repository paths, extracted archive paths, temporary directories, or user-controlled configuration). Versions 5.4.51, 6.4.33, 7.3.11, 7.4.5, and 8.0.5 contains a patch for the issue. Some workarounds are available. Avoid running PHP/ones own tooling from MSYS2-based shells on Windows; prefer cmd.exe or PowerShell for workflows that spawn native executables. Avoid passing paths containing = (and similar MSYS2-sensitive characters) to Symfony Process when operating under Git Bash/MSYS2. Where applicable, configure MSYS2 to disable or restrict argument conversion (e.g. via MSYS2_ARG_CONV_EXCL), understanding this may affect other tooling behavior.
Weakness
The product constructs a string for a command to be executed by a separate component in another control sphere, but it does not properly delimit the intended arguments, options, or switches within that command string.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Symfony | Sensiolabs | * | 5.4.51 (excluding) |
| Symfony | Sensiolabs | 6.4.0 (including) | 6.4.33 (excluding) |
| Symfony | Sensiolabs | 7.3.0 (including) | 7.3.11 (excluding) |
| Symfony | Sensiolabs | 7.4.0 (including) | 7.4.5 (excluding) |
| Symfony | Sensiolabs | 8.0.0 (including) | 8.0.5 (excluding) |
Extended Description
When creating commands using interpolation into a string, developers may assume that only the arguments/options that they specify will be processed. This assumption may be even stronger when the programmer has encoded the command in a way that prevents separate commands from being provided maliciously, e.g. in the case of shell metacharacters. When constructing the command, the developer may use whitespace or other delimiters that are required to separate arguments when the command. However, if an attacker can provide an untrusted input that contains argument-separating delimiters, then the resulting command will have more arguments than intended by the developer. The attacker may then be able to change the behavior of the command. Depending on the functionality supported by the extraneous arguments, this may have security-relevant consequences.
Potential Mitigations
- Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- Inputs should be decoded and canonicalized to the application’s current internal representation before being validated (CWE-180, CWE-181). Make sure that your application does not inadvertently decode the same input twice (CWE-174). Such errors could be used to bypass allowlist schemes by introducing dangerous inputs after they have been checked. Use libraries such as the OWASP ESAPI Canonicalization control.
- Consider performing repeated canonicalization until your input does not change any more. This will avoid double-decoding and similar scenarios, but it might inadvertently modify inputs that are allowed to contain properly-encoded dangerous content.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/137.html
- https://cwe.mitre.org/data/definitions/174.html
- https://cwe.mitre.org/data/definitions/41.html
- https://cwe.mitre.org/data/definitions/460.html
- https://cwe.mitre.org/data/definitions/88.html
References
- https://github.com/symfony/symfony/commit/35203939050e5abd3caf2202113b00cab5d379b3
- https://github.com/symfony/symfony/commit/ec154f6f95f8c60f831998ec4d246a857e9d179b
- https://github.com/symfony/symfony/issues/62921
- https://github.com/symfony/symfony/pull/63164
- https://github.com/symfony/symfony/security/advisories/GHSA-r39x-jcww-82v6