Summary
Saloon has insecure deserialization in AccessTokenAuthenticator
Description
The Saloon PHP library 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 removes PHP serialization from the AccessTokenAuthenticator class requiring users to store and resolve the authenticator manually.
Credits
Saloon thanks @HuajiHD for finding the issue and recommending solutions and @jonpurvis for applying the fix.
Impact
Users of the OAuth2 utilities in Saloon, specifically the AccessTokenAuthenticator class.
Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect. Typical impact: arbitrary code execution or logic abuse.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Upgrade guide: https://docs.saloon.dev/upgrade/upgrading-from-v3-to-v4
Frequently Asked Questions
- What is CVE-2026-33942? CVE-2026-33942 is a high-severity insecure deserialization vulnerability in saloonphp/saloon (composer), affecting versions < 4.0.0. It is fixed in 4.0.0. Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect.
- Which versions of saloonphp/saloon are affected by CVE-2026-33942? saloonphp/saloon (composer) versions < 4.0.0 is affected.
- Is there a fix for CVE-2026-33942? Yes. CVE-2026-33942 is fixed in 4.0.0. Upgrade to this version or later.
- Is CVE-2026-33942 exploitable, and should I be worried? Whether CVE-2026-33942 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-33942 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-33942? Upgrade
saloonphp/saloonto 4.0.0 or later.