Security: add allowed_classes to Form::getSessionValidationResult() unserialize()#11985
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Security: add allowed_classes to Form::getSessionValidationResult() unserialize()#11985XananasX7 wants to merge 1 commit into
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…nserialize()
Form::getSessionValidationResult() deserializes a ValidationResult object
stored in the user session without restricting allowed_classes. Since PHP
session data can be influenced by an attacker (e.g. session fixation,
session storage compromise, or a separate injection bug), this creates a
PHP Object Injection (POI) vector where an attacker can craft a serialized
payload containing arbitrary class instances.
The deserialized value is always expected to be a ValidationResult, so add
an explicit allowed_classes allowlist:
unserialize($resultData, ['allowed_classes' => [ValidationResult::class]])
This limits instantiation to only the expected class, preventing exploitation
via gadget chains even if an attacker controls the session content.
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Summary
Add explicit
allowed_classesrestriction to theunserialize()call inForm::getSessionValidationResult().Vulnerability
Form::getSessionValidationResult()(Form.php line 505) deserializes aValidationResultfrom session storage without anallowed_classesrestriction:The session data is user-controlled (read from
FormInfo.{FormName}.resultin the user's session). An attacker who can control session contents — via session fixation, a storage backend compromise, or a chained injection bug — can supply a crafted serialized payload that instantiates arbitrary PHP classes, exploiting gadget chains present in the application's dependencies.Fix
Restrict deserialization to only the expected class:
The deserialized value is always expected to be a
ValidationResult. ThesetSessionValidationResult()method on the same class only ever stores aValidationResultobject, confirming the allowlist is complete.References
allowed_classes: https://www.php.net/manual/en/function.unserialize.php