CVE-2026-81905Network attack vector

Account takeover via cross-purpose validation hash redemption

Published Sep 10, 2026 · Updated Sep 10, 2026

Authentication bypass in Concrete CMS 5.0.0 through 9.5.2 allows remote attackers with a valid validation hash to reset a user's password. The authentication controller's change_password and validation endpoints called UserInfoRepository::getByValidationHash without requiring the hash's stored purpose type. Possession of a hash from a separate disclosure channel is required; cross-purpose redemption can take over the associated account or activate it.

CVSS severity6.3
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Concrete CMS 5.0.0 through 9.5.2 allows remote attackers with a valid validation hash to reset a user's password. The authentication controller's change_password and validation endpoints called UserInfoRepository::getByValidationHash without requiring the hash's stored purpose type. Possession of a hash from a separate disclosure channel is required; cross-purpose redemption can take over the associated account or activate it.

The record

CVE
CVE-2026-81905
Published
Sep 10, 2026
Updated
Sep 10, 2026
Vendor
Concrete CMS
Product
Concrete CMS
Classifications
CWE-640, CWE-863, T1098
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.0.0 <=9.5.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Concrete CMS · Concrete CMSversion=5.0.0 <=9.5.2

Published CVSS scores

6.3Concrete CMS security teamCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-640Weak Password Recovery Mechanism for Forgotten Password
CWE-863Incorrect Authorization
T1098Account Manipulation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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