PatchTheCVECVE-2026-81906: Concrete CMS OAuth callback login path prior to version 9.5.3 did not check whether an account was active or e
CVE-2026-81906 is a medium-severity flaw (CVSS 6.3) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Concrete CMS OAuth callback login path prior to version 9.5.3 did not check whether an account was active or email-validated before establishing a session. A deactivated or unvalidated user with an existing OAuth binding could complete authentication and receive a session that was fully authenticated for the callback response, with the login recorded and login events dispatched. The Concrete CMS security team gave this vulnerability a CVSS v4.0 s
Why this priority
- Remotely exploitable, no login, no user action
No fix is published yet: follow the downgrade or mitigation steps.
Risk facts
| CVSS score | 6.3 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.6% (top 51%) |
| CISA exploited list | No |
| Weakness | CWE-288 |
| Published | 2026-09-11 |
| Last modified | 2026-09-11 |
Last updated 2026-09-11 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-81906?
No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.
Is CVE-2026-81906 being exploited?
CVE-2026-81906 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-81906 affect?
CVE-2026-81906 affects affected software. Severity is medium (CVSS 6.3). Concrete CMS OAuth callback login path prior to version 9.5.3 did not check whether an account was active or email-validated before establishing a session. A deactivated or unvalidated user with an existing OAuth binding could complete auth
How urgent is CVE-2026-81906?
Priority 39/100. Remotely exploitable, no login, no user action