Grav vulnerable to Denial of Service via Improper Input Handling in 'Supported' Parameter

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2025-66305: 0.41% estimated exploitation activity in the next 30 days; percentile 35.71 (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.

Endpoint: admin/config/system Submenu: Languages Parameter: Supported Application: Grav v 1.7.48 --- Summary A Denial of Service (DoS) vulnerability was identified in the "Languages" submenu of the Grav admin configuration panel (/admin/config/system). Specifically, the Supported parameter fails to properly validate user input. If a malformed value is inserted—such as a single forward slash (/) or an XSS test string—it causes a fatal regular expression parsing error on the server. This leads to application-wide failure due to the use of the pregmatch() function with an improperly constructed regular expression, resulting in the following error: pregmatch(): Unknown modifier 'o' File: /system/src/Grav/Common/Language/Language.php line 244 Once triggered, the site becomes completely unavailable to all users. --- Details - Vulnerable Endpoint: POST /admin/config/system - Submenu: Languages - Parameter: Supported The application dynamically constructs a regular expression using the…

Published by the source

2 Dec 2025, 00:46 UTC

Last modified by the source

2 Dec 2025, 00:46 UTC

Source last checked

26 Oct 2026, 14:35 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-m8vh-v6r6-w7p6

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# Patch Next advisory brief: CVE-2025-66305

Advisory: Grav vulnerable to Denial of Service via Improper Input Handling in 'Supported' Parameter
IDs: CVE-2025-66305, GHSA-m8vh-v6r6-w7p6
Record: https://patchnext.com/advisories/cve-2025-66305 (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 8.2)
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-m8vh-v6r6-w7p6 (GitHub-reviewed advisory GHSA-m8vh-v6r6-w7p6 lists affected ranges: Packagist getgrav/grav >=0 <1.8.0-beta.27)

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