RCE in Silverstripe Silverstripe-Userforms
CVE-2026-54721
Silverstripe UserForms provides a visual form builder for the Silverstripe CMS. From 6.0.0 until 6.4.9, 7.0.7, and 7.1.1, the userform email recipient subject field in the CMS accepts a specially crafted payload that can be interpreted as executable server-side code. An authenticated CMS user with permission to configure a UserForms email recipient can use the subject field to run arbitrary code on the server, compromising confidentiality, integrity, and availability. This issue is fixed in versions 6.4.9, 7.0.7, and 7.1.1.
Vulnerability class: RCE (Remote Code Execution)
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
Affected products
- Silverstripe Silverstripe-userforms — versions < 6.4.9, >= 7.0.0, < 7.0.7, >= 7.1.0, < 7.1.1
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_CONFIRM)
Frequently asked questions
- What is CVE-2026-54721?
- CVE-2026-54721 is a high-severity vulnerability in Silverstripe Silverstripe-Userforms, classified under Code Injection. CVSS score: 8.8/10. Published 2026-08-27.
- How severe is CVE-2026-54721?
- High severity. CVSS v3 base score is 8.8 out of 10.