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Deserialization of Untrusted DataWeakness · CWE-502

CVE-2026-10721

HIGH · 8.4 CVSS v4.0 Published 2026-06-10
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
86/100
Remediation priority · High
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Concrete CMS below 9.5.2 is vulnerable to PHP Object Injection via unserialize() calls in the  in Permission, Cache, and Search components. An unauthenticated attacker may trigger arbitrary PHP object instantiation if a malicious serialized payload has been placed in the database. Thanks XananasX7 for reporting.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Concrete CMS versions below 9.5.2 are vulnerable to PHP Object Injection through unsafe unserialize() calls in the Permission, Cache, and Search components. An unauthenticated attacker can trigger arbitrary PHP object instantiation if they have pre-planted a malicious serialized payload in the database, potentially leading to remote code execution depending on available PHP gadget chains.

MitigationUpgrade Concrete CMS to version 9.5.2 or later to patch the unsafe unserialize() calls. Additionally, audit the database for any unauthorized malicious serialized payloads that may have been inserted.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
High
Authentication
X
User interaction
None
Scope
X

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Concrete CMS version
    Access the Concrete CMS dashboard or check the version file in the installation directory. Common locations include the dashboard 'Welcome' page or a version.php file in the application config.
    Affected if The installed version is below 9.5.2 (e.g., 9.5.1, 9.5.0, 9.x versions prior to 9.5.2, or any 8.x version).
  2. Verify database access controls
    Review database user permissions and network access. Ensure that the database is not directly exposed and that application database credentials follow least-privilege principles.
    Affected if The database is accessible to untrusted users or the application database user has more privileges than required for normal operation.
  3. Confirm database write access is restricted
    Audit database access logs and application configurations to verify that unauthenticated or low-privilege users cannot insert or modify records in core tables.
    Affected if Untrusted actors can write arbitrary data to the database, which is required for placing the malicious serialized payload.
  4. Review application logging for suspicious database activity
    Examine Concrete CMS and database logs for unusual INSERT or UPDATE operations, especially in the Permission, Cache, or Search related tables.
    Affected if Logs show unauthorized or unexpected database modifications, particularly involving serialized data.

A Concrete CMS installation is affected if its version is below 9.5.2 AND an attacker can inject serialized PHP objects into the database.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Concrete CMS to version 9.5.2 or later to patch the unsafe unserialize() calls. Additionally, audit the database for any unauthorized malicious serialized payloads that may have been inserted.

Recommended fix High confidence

Concrete CMS 9.5.2

  1. Backup the existing Concrete CMS site, including all files and the database
  2. Download Concrete CMS version 9.5.2 from the official source (concretecms.com or documentation.concretecms.org)
  3. If using a manual installation, replace the core files with the new version while preserving the /application/config/ and /packages/ directories
  4. If using composer, run 'composer update concretecms/concrete-cms' to get version 9.5.2
  5. Run any database migrations required for the upgrade (typically via the dashboard or CLI tool)
  6. Clear all caches after the upgrade to ensure no stale cached objects remain
  7. Verify the upgrade was successful by logging into the admin dashboard
Caveat Review release notes for 9.5.2 for any breaking changes or configuration requirements before upgrading; test in a staging environment first

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,980
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-10721 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data