CVE-2026-33942
PHP Object Injection in Saloon Library Enables Remote Code Execution
Publication date: 2026-03-26
Last updated on: 2026-03-26
Assigner: GitHub, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| saloon | saloon | to 4.0.0 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-502 | The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
CVE-2026-33942 is a high-severity vulnerability in the Saloon PHP library versions prior to 4.0.0. It occurs in the AccessTokenAuthenticator class, which uses PHP's unserialize() function with allowed_classes set to true to restore OAuth token state from cache or storage.
An attacker who can control the serialized input—such as by overwriting cached token files or through injection—can supply a malicious serialized "gadget" object. When unserialize() processes this input, PHP instantiates the object and executes its magic methods (__wakeup, __destruct, etc.), leading to object injection.
In environments with common dependencies like Monolog, this vulnerability can be chained to achieve remote code execution (RCE). The issue is classified under CWE-502 (Deserialization of Untrusted Data).
The fix in Saloon version 4.0.0 removes the use of PHP serialization in the AccessTokenAuthenticator class, requiring users to manually store and resolve the authenticator instead.
How can this vulnerability impact me? :
This vulnerability can allow an attacker who can control serialized input to perform object injection, which in certain environments can lead to remote code execution (RCE).
Remote code execution means an attacker could run arbitrary code on your system, potentially leading to full system compromise, data theft, or disruption of services.
How can this vulnerability be detected on my network or system? Can you suggest some commands?
This vulnerability arises from the use of PHP's unserialize() function with allowed_classes set to true in the AccessTokenAuthenticator::unserialize() method in Saloon versions prior to 4.0.0. Detection involves identifying if your system is running a vulnerable version of the Saloon PHP library and if the AccessTokenAuthenticator class is used to restore OAuth token state from cache or storage.
You can check the installed version of Saloon in your project by running the following command in your project directory:
- composer show saloonphp/saloon
If the version is prior to 4.0.0, your system is potentially vulnerable.
Additionally, you can search your codebase or cache storage for usage of unserialize() in AccessTokenAuthenticator or look for cached token files that might be overwritten or injected with malicious serialized objects.
For example, to find usage of unserialize in your code, you can run:
- grep -r 'unserialize' path/to/your/project
To check for suspicious modifications or overwrites of cached token files, monitor file changes or audit logs related to the cache directory used by Saloon.
What immediate steps should I take to mitigate this vulnerability?
The primary and recommended mitigation is to upgrade the Saloon PHP library to version 4.0.0 or later, where the vulnerability is fixed by removing the use of PHP serialization in the AccessTokenAuthenticator class.
Until you can upgrade, avoid using versions prior to 4.0.0 and do not allow untrusted input to control serialized data used by AccessTokenAuthenticator.
Additionally, review and secure your cache or storage mechanisms to prevent attackers from overwriting or injecting malicious serialized objects.
Follow the official upgrade guide at https://docs.saloon.dev/upgrade/upgrading-from-v3-to-v4 to ensure a smooth and secure transition.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
The vulnerability in Saloon PHP library allows remote code execution through object injection by exploiting unsafe deserialization of OAuth token data. This can lead to unauthorized access or control over systems handling sensitive data.
Such unauthorized access or potential data breaches can negatively impact compliance with common standards and regulations like GDPR and HIPAA, which require strict controls over data confidentiality, integrity, and system security.
Therefore, if exploited, this vulnerability could result in violations of these regulations due to compromised data security and privacy.