typo3/cms-core security advisory

CVE-2026-49740: TYPO3-CORE-SA-2026-018: Insecure Deserialization in Core API

CVE-2026-49740 is a medium-severity PHP object injection vulnerability in the PHP package typo3/cms-core (CVSS 6.3), published 9 June 2026. It is fixed in 10.4.57, 11.5.51, 12.4.46, 13.4.31 and 14.3.3, one per release line; earlier versions on each line are affected. Exploiting it needs a low-privilege user account.

medium 6.3 published 2026-06-09 · updated 2026-07-23

Affected versions: < 10.4.57
>= 11.0.0, < 11.5.51
>= 12.0.0, < 12.4.46
>= 13.0.0, < 13.4.31
>= 14.0.0, < 14.3.3
Fixed in: 10.4.57, 11.5.51, 12.4.46, 13.4.31, 14.3.3
Newest release: 14.3.10
Severity: Medium · CVSS 6.3
Type: PHP object injection
CWE-502
Exploited in the wild: Not on the CISA KEV list
checked 2026-11-04

Is your typo3/cms-core version affected?

Run composer show typo3/cms-core in your project, then enter the version. We check it against this and every other known typo3/cms-core advisory.

Who can exploit CVE-2026-49740

Access: A normal, low-privilege user account in the app.
Position: The attacker needs local access to the server.

CVSS vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:H/SI:H/SA:H

Your app is only exposed if it uses the affected part of typo3/cms-core. The advisory below says which part that is. If you are not sure, upgrade anyway: it costs less than finding out.

How to fix CVE-2026-49740 in typo3/cms-core

Find the installed version: composer show typo3/cms-core. If you never required it yourself, composer why typo3/cms-core shows which package pulls it in.
Update it: composer update typo3/cms-core --with-all-dependencies. You need the fixed version for your release line (10.4.57, 11.5.51, 12.4.46, 13.4.31 and 14.3.3).
If Composer will not go that high, your composer.json constraint is holding it back. Widen it (for example "typo3/cms-core": "^14.3.3" if you can take that version), or upgrade the package that requires it.
Run composer audit. It reads the same advisory data and should no longer list CVE-2026-49740.
Commit composer.lock and deploy it. On the server, run composer install --no-dev from the lock file, not composer update.

If you cannot upgrade yet

General hardening for PHP object injection issues while the upgrade waits. None of it replaces the fix.

Never pass user-controlled data to unserialize() or to template rendering, and restrict who can edit templates or settings.
Put a web application firewall in front of the app and watch for new PHP files or admin users.
If your app does not use the affected feature, note that in your audit, but still plan the upgrade.

The CVE-2026-49740 advisory

TYPO3's cache frontend (VariableFrontend) and persistent key-value store (Registry) deserialized PHP payloads without integrity validation or class restrictions. An attacker with write access to the underlying storage backend (cache store or sys_registry database table) could inject a crafted serialized payload to trigger PHP Object Injection, potentially exploiting a gadget chain to achieve Remote Code Execution or other high-impact effects. Exploiting this vulnerability requires direct local write access to the storage, such as the SQL database or file system. This issue affects TYPO3 CMS versions before 10.4.57, 11.0.0-11.5.50, 12.0.0-12.4.45, 13.0.0-13.4.30 and 14.0.0-14.3.2.

Description from the CVE record, via the NVD entry for CVE-2026-49740. Advisory title: “TYPO3-CORE-SA-2026-018: Insecure Deserialization in Core API”.

References

Other typo3/cms-core advisories

high CVE-2026-19418: TYPO3-CORE-SA-2026-021: Broken Access Control in Backend and Install Tool 2026-08-11
high CVE-2026-11607: TYPO3-CORE-SA-2026-019: Broken Access Control in Form Framework 2026-06-09
high CVE-2026-49741: TYPO3-CORE-SA-2026-017: Privilege Escalation & SQL Injection in Form Framework 2026-06-09
low CVE-2026-49738: TYPO3-CORE-SA-2026-016: Broken Access Control in File Abstraction Layer 2026-06-09
medium CVE-2026-47352: TYPO3-CORE-SA-2026-015: Broken Access Control in Backend API 2026-06-09
medium CVE-2026-47351: TYPO3-CORE-SA-2026-014: Broken Access Control in Clipboard 2026-06-09

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Where this data comes from

Affected and fixed versions: the Packagist security advisories API (GitHub Advisory Database and FriendsOfPHP), the same data composer audit uses. Synced 2026-11-03.
Description, score, weakness and references: NIST National Vulnerability Database (NVD), checked 2026-11-04. This product uses data from the NVD API but is not endorsed or certified by the NVD.
Exploited-in-the-wild status: the CISA Known Exploited Vulnerabilities catalog, checked 2026-11-04.
Compiled by Daniel Lasek at Laskyr from the sources above. The summary, “who can exploit it”, “how to fix it” and hardening sections are our plain-English reading of the record and are generated from it. The quoted description is the record's own text. Spot an error? Tell us.