CVE-2026-7888 Concrete CMS is vulnerable to PHP Object Injection via unserialize() calls in the Workflow, Form block, and File/Set components
Unauthenticated attackers can trigger arbitrary PHP object instantiation via unsafe deserialization in Concrete CMS components.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-7888?
CVE-2026-7888 is a high-severity unsafe deserialization vulnerability in Concrete CMS, published on 3 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Concrete CMS below 9.5.3 is vulnerable to PHP Object Injection via unserialize() calls in the Workflow, Form block, and File/Set components that lack the allowed_classes restriction. The Form block and File/Set sinks were addressed in 9.5.2; the Workflow component sinks were addressed in 9.5.3. An unauthenticated attacker may trigger arbitrary PHP object instantiation if a malicious serialized payload has been placed in the database. Thanks XananasX7 and Sanjorn Keeratirungsan (dizconnect) for independently reporting the original components, and sh4d0byss for reporting the Workflow component wasn't fixed in 9.5.2. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 8.4 with vector CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/ VC:H/VI:H/VA:H/SC:N/SI:N/SA:N.
Weakness: CWE-502
Which versions are affected by CVE-2026-7888?
2 open source packages ship an affected version, including concrete5/concrete5.
| Package | Affected | Fixed in |
|---|---|---|
concrete5/concrete5 Packagist | All versions | 9.5.2 |
concrete5/concrete5 Packagist | All versions | 9.5.2 |
How do I fix CVE-2026-7888?
Upgrade concrete5/concrete5 to 9.5.2 or later.
Upgrade, and only deserialise data from trusted sources or with an allow-list of types. More about Unsafe deserialization.
Is CVE-2026-7888 being exploited?
There is no known exploitation of CVE-2026-7888 in the wild and no public exploit code.
Sources
Also known as GHSA-52pr-7vmf-2w7x.