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🛡️ CVE-2026-8134 — concrete-cms

🔴 CVSS 9.5 — Critical ✅ No Known Exploit CWE-23 NVD
9.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Concrete CMS 9.5.0 and below fails to sanitize path traversal sequences in the ptComposerFormLayoutSetControlCustomTemplate field when saving page type composer form layouts. An authenticated rogue administrator with composer form editing rights can exploit this to include arbitrary readable files on the server. Combined with the file uploader's extension-only validation (which permits PHP code in files saved with image extensions like .png), this can result in authenticated remote code execution. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 9.4 with vector CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H   Thanks Yonatan Drori (Tenzai) for reporting.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs administrative privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: High — administrative rights are needed first.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2026-8134 is classified as CWE-23: Relative Path Traversal. Relative path sequences in user input are not neutralised, so requests can climb out of the intended directory.

Affected software

CVE-2026-8134 is recorded against 2 packages.

  • concrete-cms (fixed in 9.5.0)
  • concrete5/concrete5 (fixed in 9.5.1)

Timeline and source

Published on 21 May 2026 and last revised on 23 July 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

documentation.concretecms.org

Other advisories for this package

concrete-cms has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-23: Relative Path Traversal) in other software:

Details

Severity HIGH
CVSS Score 9.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
CWE CWE-23
Public Exploit ✅ No
Source NVD
Published 2026-05-21
Updated 2026-08-20
Modified 2026-07-23
Fix URL N/A

Affected Packages

Software From version Fixed in
concrete-cms — 9.5.0
concrete5/concrete5 — 9.5.1

Similar Threats

Exploit Protection

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CVE-2026-8134 carries CVSS 9.5 Critical rating. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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