Concrete CMS: Deserialization of Untrusted Data
CVE-2026-3452 is a high-severity deserialization of untrusted data vulnerability in Concrete CMS, with a CVSS 3.1 base score of 7.2 out of 10. It can be exploited remotely over the network by an attacker with administrator privileges, without any action from a user. The record lists version 9.4.8 as the first without the flaw, so updating Concrete CMS to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.69% chance of exploitation within 30 days, higher than 53% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Concrete CMS to 9.4.8 or a later version.
- Read the advisory on documentation.concretecms.org for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Concrete CMS | Concrete CMS | 5 up to, but not including, 9.4.8 | 9.4.8 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- HighAdministrator-level access is required first.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.9 | High | CNA |
| CVSS 3.1 | 7.2 | High | NVD |
Official description
Concrete CMS below version 9.4.8 is vulnerable to Remote Code Execution by stored PHP object injection into the Express Entry List block via the columns parameter. An authenticated administrator can store attacker-controlled serialized data in block configuration fields that are later passed to unserialize() without class restrictions or integrity checks. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 8.9 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H. Thanks YJK ( @YJK0805 https://hackerone.com/yjk0805 ) of ZUSO ART https://zuso.ai/ for reporting.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Deserialization of Untrusted Data
The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.
How developers prevent this class of flaw
- If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.
- When deserializing data, populate a new object rather than just deserializing. The result is that the data flows through safe input validation and that the functions are safe.
- Explicitly define a final object() to prevent deserialization.
More Deserialization of Untrusted Data vulnerabilities (CWE-502)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in Concrete CMS
- 7.1 High severity
- 9.6 Critical severity
- 7.1 High severity
- 7.1 High severity
- 7.3 High severity
- 7.5 High severity
Recent Deserialization of Untrusted Data vulnerabilities
- 10.0 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
- 7.2 High severity
- 9.8 Critical severity
- 7.5 High severity
Spotted an error? Tell us.