CVE-2026-54721: Silverstripe/userforms Remote Code Execution Vulnerability
HIGHCVE-2026-54721 is a HIGH (CVSS 8.8) remote code execution vulnerability (CWE-94: Improper Control of Generation of Code ('Code Injection')) affecting Silverstripe/userforms libraries in the Packagist ecosystem. The issue involves silverstripe/userforms vulnerable to remote code execution via userforms email subject. Remediation is available by upgrading affected packages to version 6.4.9, 7.0.7, 7.1.1.
CVE-2026-54721 at a Glance
Security Impact
CVSS: 8.8
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).
How to Fix CVE-2026-54721
To remediate this vulnerability, upgrade all affected Silverstripe/userforms dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
Upgrade silverstripe/userforms to 6.4.9Upgrade silverstripe/userforms to 7.0.7Upgrade silverstripe/userforms to 7.1.1Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for silverstripe/userformsHow to Check if You Are Affected
To determine whether your application is affected by CVE-2026-54721, inspect your project dependencies for Silverstripe/userforms:
inspect dependencies for silverstripe/userformsAnalyze the terminal output to locate any version of Silverstripe/userforms in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 6.4.9), your application is affected.
Note: Verify declared build manifests and deployed runtime container environments.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-94: Improper Control of Generation of Code ('Code Injection'), where the product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. In Silverstripe/userforms, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-54721 Affected Silverstripe/userforms Versions
3 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
silverstripe/userforms
|
Packagist |
< 6.4.9
|
6.4.9
|
|
silverstripe/userforms
|
Packagist |
≥ 7.0.0
< 7.0.7
|
7.0.7
|
|
silverstripe/userforms
|
Packagist |
≥ 7.1.0
< 7.1.1
|
7.1.1
|
References
Frequently Asked Questions
What is CVE-2026-54721?
Which Silverstripe/userforms versions are affected?
What version fixes CVE-2026-54721?
Is silverstripe/userforms affected?
What is the CVSS score of CVE-2026-54721?
What CWE is associated with CVE-2026-54721?
How can I check Packagist dependencies for CVE-2026-54721?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-g8wr-r2v2-vqc6",
"modified" : "2026-08-27T16:53:18Z",
"published" : "2026-08-27T16:53:17Z",
"aliases" : [ "CVE-2026-54721" ],
"summary" : "silverstripe/userforms vulnerable to remote code execution via userforms email subject",
"details" : "### Impact\nThe userform email subject field in the CMS is vulnerable to a specially crafted payload being used to run arbitrary code on the server.\n\n### Reported by\nJack Wallace from Bastion Security",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Packagist",
"name" : "silverstripe/userforms"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "6.4.9"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Packagist",
"name" : "silverstripe/userforms"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "7.0.0"
}, {
"fixed" : "7.0.7"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Packagist",
"name" : "silverstripe/userforms"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "7.1.0"
}, {
"fixed" : "7.1.1"
} ]
} ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/silverstripe/silverstripe-userforms/security/advisories/GHSA-g8wr-r2v2-vqc6"
}, {
"type" : "WEB",
"url" : "https://github.com/silverstripe/silverstripe-userforms/pull/1441"
}, {
"type" : "WEB",
"url" : "https://github.com/silverstripe/silverstripe-userforms/pull/1442"
}, {
"type" : "WEB",
"url" : "https://github.com/silverstripe/silverstripe-userforms/commit/23c069866900c19b499bfa997d1e251e97491702"
}, {
"type" : "WEB",
"url" : "https://github.com/silverstripe/silverstripe-userforms/commit/c55494ad7c717b199a3c1663b43a54db5d95604c"
}, {
"type" : "WEB",
"url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/silverstripe/userforms/CVE-2026-54721.yaml"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/silverstripe/silverstripe-userforms"
}, {
"type" : "WEB",
"url" : "https://github.com/silverstripe/silverstripe-userforms/releases/tag/6.4.9"
}, {
"type" : "WEB",
"url" : "https://github.com/silverstripe/silverstripe-userforms/releases/tag/7.0.7"
}, {
"type" : "WEB",
"url" : "https://github.com/silverstripe/silverstripe-userforms/releases/tag/7.1.1"
}, {
"type" : "WEB",
"url" : "https://www.silverstripe.org/download/security-releases/cve-2026-54721"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-20", "CWE-94" ],
"severity" : "HIGH",
"github_reviewed" : true,
"github_reviewed_at" : "2026-08-27T16:53:17Z",
"nvd_published_at" : null
}
}