CVE-2026-8134
CVE-2026-8134 is a high-severity vulnerability in Concretecms Concrete Cms with a CVSS 3.x base score of 7.2. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-23.
Key facts
- Severity: High (CVSS 3.x base score 7.2)
- CVSS v4: 9.4
- EPSS exploit prediction: 1% (50th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-31335
- Weakness: CWE-23
- Affected product: Concretecms Concrete Cms
- Published:
- Last modified:
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.
Frequently asked questions
- What is CVE-2026-8134?
- 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 severe is CVE-2026-8134?
- CVE-2026-8134 has a CVSS 3.x base score of 7.2, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
- Is CVE-2026-8134 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-8134?
- CVE-2026-8134 affects Concretecms Concrete Cms. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2026-8134?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- Does CVE-2026-8134 have an EU (EUVD) identifier?
- Yes. CVE-2026-8134 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-31335.
- When was CVE-2026-8134 published?
- CVE-2026-8134 was published on 2026-05-21 and last updated on 2026-06-17.
References
Affected products (1)
- cpe:2.3:a:concretecms:concrete_cms:*:*:*:*:*:*:*:*
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