CVE-2026-46725: TYPO3 Remote Code Execution in extension "Content Element Selector" (ceselector)

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 1.9%, percentile 79: FIRST’s model estimates a 1.9% chance of exploitation activity in the next 30 days, higher than 79% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes mmc/ceselector (Composer (PHP)) >= 6.0.0, < 6.0.1, fixed in 6.0.1; mmc/ceselector (Composer (PHP)) >= 5.0.0, < 5.0.1, fixed in 5.0.1; mmc/ceselector (Composer (PHP)) >= 4.0.0, < 4.0.2, fixed in 4.0.2; mmc/ceselector (Composer (PHP)) < 3.0.3, fixed in 3.0.3. Check your lockfile, including transitive dependencies.

What it is

The extension passes an attacker-controlled cookie directly to PHP's unserialize() without safely processing the input. A remote, unauthenticated attacker can supply a crafted serialized payload to trigger PHP Object Injection, leading to Remote Code Execution on the TYPO3 server. Exploitation requires the content element to be configured with "Persistent Mode: Static" in the plugin settings.

From the GitHub advisory

The TYPO3 "Content Element Selector" (ceselector) extension passes an attacker-controlled cookie directly to PHP's unserialize() without safely processing the input. A remote, unauthenticated attacker can supply a crafted serialized payload to trigger PHP Object Injection, leading to Remote Code Execution on the TYPO3 server. Exploitation requires the content element to be configured with Persistent Mode: Static in the plugin settings. This has been patched in version 3.0.3, 4.0.2, 5.0.1, and 6.0.1.

Weakness type: CWE-502.

Product: mmc/ceselector (Composer (PHP)) · Assigned by: TYPO3 · Published: 2026-05-19

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: present (depends on deployment conditions)
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 1.86% probability of exploitation activity in the next 30 days; percentile 79.

Timeline

• 2026-05-19 — CVE record last updated
• 2026-05-19 — CVE record published by TYPO3
• 2026-05-19 — GitHub-reviewed advisory GHSA-8x3j-439w-537c published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. typo3.org typo3.org

Vulnerability records

1. GitHub Advisory GHSA-8x3j-439w-537c github.com
2. CVE.org record CVE-2026-46725 cve.org
3. NVD entry CVE-2026-46725 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com

Critical Composer (PHP) advisories · Today’s Security Digest