[UNREVIEWED] OAuth Callback Login Bypasses Deactivated-Account Checks
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 score of 6.3 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.
- Published
- Sep 10, 2026
- Updated
- Sep 11, 2026
- EPSS
- 0.6% · 48th percentile
- CWE
- CWE-288
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Report tools
Action score
25
Monitor
Low priority for now.
- CVSS
- 25 / 40 · 6.3 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.6%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · ConcreteCMS
- 6.3
- NVD has not scored this yet; the score shown is the CNA’s.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpAffected systems
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (ConcreteCMS). Independent of NVD's CPE analysis and usually ahead of it.
Concrete CMS Concrete CMS
- 5.0.0 and later · up to and including 9.5.2affected · git
Same product
concrete cms: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-18111Concrete CMS below 9.5.4 allows privilege escalation because adding users and assigning groups do not require additional identity verification34Monitor
- CVE-2026-10721Concrete CMS below 9.5.2 is vulnerable to PHP Object Injection via unserialize() calls in the in Permission, Cache, and Search components33Monitor
- CVE-2026-7888Concrete 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 allowe33Monitor
- CVE-2026-81898Concrete CMS below version 9.5.3 is vulnerable to Stored XSS via country-less Address attribute in Express association views30Monitor
- CVE-2026-18113Concrete CMS 9.0 to 9.5.2 is vulnerable to Stored XSS in the Top Navigation Bar Block via Dropdown Child Page Names30Monitor
- CVE-2026-81899Concrete CMS 9.0 to 9.5.2 is vulnerable to Stored XSS via group folder name on the Members > Groups dashboard29Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
No fix version is recorded for this entry. Check the references for vendor advisories.
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
- tenzaifinder
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
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Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
- CVE-2026-1072192 days apartConcrete CMS below 9.5.2 is vulnerable to PHP Object Injection via unserialize() calls in the in Permission, Cache, and Search components33Monitor
- CVE-2026-788899 days apartConcrete 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 allowe33Monitor
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- Integrity
- Availability
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- X
Weakness class (CWE)
CWE-288 · Authentication Bypass Using an Alternate Path or ChannelCVSS vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/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
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
Change log
No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.
References
Vendor advisories and official records. Exploit/PoC links are deliberately left out.