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High, CVSS 8.1

TYPO3 Possible Insecure Deserialization in Extbase Request Handling

GHSA-5h5v-m596-r6rf

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (typo3/cms-core 9.5.12, 8.7.30), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • Packagist typo3/cms-core

    Affected
    >= 8.0.0, < 8.7.30>= 9.0.0, < 9.5.12
    Fixed in
    8.7.30, 9.5.12

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
8.1 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

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)

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-5h5v-m596-r6rf

Agent brief

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# Patch Next advisory brief: GHSA-5h5v-m596-r6rf

Advisory: TYPO3 Possible Insecure Deserialization in Extbase Request Handling
IDs: GHSA-5h5v-m596-r6rf
Record: https://patchnext.com/advisories/ghsa-5h5v-m596-r6rf (revision 1, source checked 26 Oct 2026, 14:25 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: typo3/cms-core 9.5.12, 8.7.30. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist typo3/cms-core: affected >= 8.0.0, < 8.7.30; >= 9.0.0, < 9.5.12; fixed in 8.7.30, 9.5.12

## Suggested inspection (read-only)
- Packagist typo3/cms-core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on typo3/cms-core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5h5v-m596-r6rf (GitHub-reviewed advisory GHSA-5h5v-m596-r6rf lists affected ranges: Packagist typo3/cms-core >=8.0.0 =9.0.0 <9.5.12)

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