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CVE-2026-85387— Concrete CMS before 9.5.4 allows a deactivated user to retain OAuth-authenticated REST API access

Quick assessment

Affected
Concrete CMS Concrete CMS
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Concrete CMS before 9.5.4 re-authorized OAuth REST API requests from the bearer token alone and did not re-check the state of the account the token had been issued to. The resource server's authorization validator confirmed only that a token existed, had not e

CVSS 2.0 · Low
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I. Basic Information for CVE-2026-85387

Vulnerability Information

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Vulnerability Title
Concrete CMS before 9.5.4 allows a deactivated user to retain OAuth-authenticated REST API access
Source: CVE Program / CVE List V5
Vulnerability Description
Concrete CMS before 9.5.4 re-authorized OAuth REST API requests from the bearer token alone and did not re-check the state of the account the token had been issued to. The resource server's authorization validator confirmed only that a token existed, had not expired, and had not been explicitly revoked, and deactivating a user did not revoke that user's outstanding tokens. As a result, a deactivated user retained full access to /ccm/api/1.0/* for the remaining lifetime of any token already issued to them. The same gap applied to accounts that had been deleted or locked pending a forced password reset. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.0 with vector CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N. Thanks Myq Larson for reporting.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
不充分的会话过期机制
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Concrete CMS Concrete CMS 5.0.0 ~ 9.5.3 -

II. Public POCs for CVE-2026-85387

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III. Intelligence Information for CVE-2026-85387

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Other References for CVE-2026-85387 (1)

Same Patch Batch · Concrete CMS · 2026-09-16 · 6 CVEs total

CVE-2026-85385 7.7 HIGH Concrete CMS below 9.5.4 is vulnerable to Stored XSS via User Timezone Field
CVE-2026-85386 7.3 HIGH Concrete CMS before 9.5.4 stored is vulneratble to cross-site scripting via unauthenticate
CVE-2026-18120 6.3 MEDIUM Missing Authorization in legacy Express entries search endpoint allows disclosure of Expre
CVE-2026-87028 5.3 MEDIUM Cross-Board IDOR in the Board Custom Slot Preview in Concrete CMS 9.0.0 through 9.5.3 Disc
CVE-2026-87031 2.1 LOW Missing authorization in the REST API user creation endpoint in Concrete CMS 9.2.0 through

IV. Related Vulnerabilities

Same product: Concrete CMS
Same vendor: Concrete CMS
Same weakness: CWE-613

V. Comments for CVE-2026-85387

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