Grav is vulnerable to RCE via SSTI through Twig Sandbox Bypass

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2025-66294: 3.02% estimated exploitation activity in the next 30 days; percentile 87.46 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A Server-Side Template Injection (SSTI) vulnerability exists in Grav that allows authenticated attackers with editor permissions to execute arbitrary commands on the server and, under certain conditions, may also be exploited by unauthenticated attackers. This vulnerability stems from weak regex validation in the cleanDangerousTwig method. Important - First of all this vulnerability is due to weak sanitization in the method clearDangerousTwig, so any other class that calls it indirectly through for example $twig-processString to sanitize code is also vulnerable. - For this report, we will need the official Form and Admin plugin installed, also I will be chaining this with another vulnerability to allow an editor which is a user with only pages permissions to edit the process section of a form. - I made another report for the other vulnerability which is a Broken Access Control which allows a user with full permission for pages to change the process section by intercepting the…

Published by the source

2 Dec 2025, 01:25 UTC

Last modified by the source

2 Dec 2025, 01:25 UTC

Source last checked

26 Oct 2026, 14:35 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-662m-56v4-3r8f

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# Patch Next advisory brief: CVE-2025-66294

Advisory: Grav is vulnerable to RCE via SSTI through Twig Sandbox Bypass
IDs: CVE-2025-66294, GHSA-662m-56v4-3r8f
Record: https://patchnext.com/advisories/cve-2025-66294 (revision 1, source checked 26 Oct 2026, 14:35 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: getgrav/grav 1.8.0-beta.27. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist getgrav/grav: affected < 1.8.0-beta.27; fixed in 1.8.0-beta.27

## Suggested inspection (read-only)
- Packagist getgrav/grav: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on getgrav/grav.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-662m-56v4-3r8f (GitHub-reviewed advisory GHSA-662m-56v4-3r8f lists affected ranges: Packagist getgrav/grav >=0 <1.8.0-beta.27)

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