CVE-2026-8417Network attack vector

Forced package upgrade via tokenless GET request

Published May 21, 2026 · Updated May 21, 2026

CSRF in Concrete CMS 9.5.0 and earlier allows remote attackers to make an administrator trigger an installed package upgrade. The do_update() method accepts a package handle from a state-changing GET request without validating a CSRF token, then calls upgradeCoreData() and upgrade(). Reachability requires an authenticated administrator with canInstallPackages() and an installed target package; the action executes that package's upgrade routines.

CVSS severity7.5
High
EPSS probability0.12%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CSRF in Concrete CMS 9.5.0 and earlier allows remote attackers to make an administrator trigger an installed package upgrade. The do_update() method accepts a package handle from a state-changing GET request without validating a CSRF token, then calls upgradeCoreData() and upgrade(). Reachability requires an authenticated administrator with canInstallPackages() and an installed target package; the action executes that package's upgrade routines.

The record

CVE
CVE-2026-8417
Published
May 21, 2026
Updated
May 21, 2026
Vendor
Concrete CMS
Product
Concrete CMS
Classifications
CWE-352, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 21, 2026CVE publishedPublication date reported by the CVE source.
  2. May 21, 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?

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  1. Affected versionversion=5.0 <=9.5.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Concrete CMS · Concrete CMSversion=5.0 <=9.5.0

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
7.5ConcreteCMSCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/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-352Cross-Site Request Forgery (CSRF)
T1204.001Malicious Link

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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