CVE-2026-33942: Saloon has insecure deserialization in AccessTokenAuthenticator (object injection / RCE)

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-26 · updated 2026-06-17
Weakness: CWE-502

Description

Saloon is a PHP library that gives users tools to build API integrations and SDKs. Versions prior to 4.0.0 used PHP's unserialize() in AccessTokenAuthenticator::unserialize() to restore OAuth token state from cache or storage, with allowed_classes => true. An attacker who can control the serialized string (e.g. by overwriting a cached token file or via another injection) can supply a serialized "gadget" object. When unserialize() runs, PHP instantiates that object and runs its magic methods (__wakeup, __destruct, etc.), leading to object injection. In environments with common dependencies (e.g. Monolog), this can be chained to remote code execution (RCE). The fix in version 4.0.0 removes PHP serialization from the AccessTokenAuthenticator class requiring users to store and resolve the authenticator manually.

Affected products

saloonphp saloon: before 4.0.0 — fixed in 4.0.0

How to fix

Upgrade to a fixed version: saloonphp saloon 4.0.0. Check the vendor advisory for mitigations.

References

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