Summary
CraftCMS has an RCE vulnerability via relational conditionals in the control panel
A Remote Code Execution vulnerability exists in the Craft CMS 5 conditions system.
The BaseElementSelectConditionRule::getElementIds() method passes user-controlled string input
through renderObjectTemplate() -- an unsandboxed Twig rendering function with escaping disabled.
Any authenticated Control Panel user (including non-admin roles such as Author or Editor) can achieve full
RCE by sending a crafted condition rule via standard element listing endpoints.
This vulnerability requires no admin privileges, no special permissions beyond basic control panel access, and
bypasses all production hardening settings (allowAdminChanges: false, devMode: false,
enableTwigSandbox: true).
Users should update to the patched 5.99 release to mitigate the issue.
Impact
Untrusted input is evaluated as executable code within the application's runtime environment. Typical impact: arbitrary code execution within the application's privilege context.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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craftcms/cms to 5.9.9 or later; craftcms/cms to 4.17.4 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-31857? CVE-2026-31857 is a high-severity code injection vulnerability in craftcms/cms (composer), affecting versions >= 5.0.0-RC1, <= 5.9.8. It is fixed in 5.9.9, 4.17.4. Untrusted input is evaluated as executable code within the application's runtime environment.
- Which versions of craftcms/cms are affected by CVE-2026-31857? craftcms/cms (composer) versions >= 5.0.0-RC1, <= 5.9.8 is affected.
- Is there a fix for CVE-2026-31857? Yes. CVE-2026-31857 is fixed in 5.9.9, 4.17.4. Upgrade to this version or later.
- Is CVE-2026-31857 exploitable, and should I be worried? Whether CVE-2026-31857 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-31857 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-31857?
- Upgrade
craftcms/cmsto 5.9.9 or later - Upgrade
craftcms/cmsto 4.17.4 or later
- Upgrade