GHSA-5H5V-M596-R6RF

It has been discovered that request handling in Extbase can be vulnerable to insecure deserialization. User submitted payload has to be signed with a corresponding HMAC-SHA1 using the sensitive TYPO3 encryptionKey as secret - invalid or unsigned payload is not deserialized.

However, since sensitive information could have been leaked by accident (e.g. in repositories or in commonly known and unprotected backup files), there is the possibility that attackers know the private encryptionKey and are able to calculate the required HMAC-SHA1 to allow a malicious payload to be deserialized.

Requirements for successfully exploiting this vulnerability (all of the following):

• rendering at least one Extbase plugin in the frontend
• encryptionKey has been leaked (from LocalConfiguration.php or corresponding .env file)

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.

GHSA-5H5V-M596-R6RF has a CVSS score of 8.1 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (8.7.30, 9.5.12); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is GHSA-5H5V-M596-R6RF? GHSA-5H5V-M596-R6RF is a high-severity insecure deserialization vulnerability in typo3/cms-core (composer), affecting versions >= 8.0.0, < 8.7.30. It is fixed in 8.7.30, 9.5.12. Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect.
2. How severe is GHSA-5H5V-M596-R6RF? GHSA-5H5V-M596-R6RF has a CVSS score of 8.1 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of typo3/cms-core are affected by GHSA-5H5V-M596-R6RF? typo3/cms-core (composer) versions >= 8.0.0, < 8.7.30 is affected.
4. Is there a fix for GHSA-5H5V-M596-R6RF? Yes. GHSA-5H5V-M596-R6RF is fixed in 8.7.30, 9.5.12. Upgrade to this version or later.
5. Is GHSA-5H5V-M596-R6RF exploitable, and should I be worried? Whether GHSA-5H5V-M596-R6RF 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
6. What actually determines whether GHSA-5H5V-M596-R6RF 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.
7. How do I fix GHSA-5H5V-M596-R6RF?
   • Upgrade typo3/cms-core to 8.7.30 or later
   • Upgrade typo3/cms-core to 9.5.12 or later