Grav's Twig processing allowing dangerous PHP functions by default

Exploitation

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

CVSS

8.4 · CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:H

EPSS

• CVE-2021-29440: 29.90% estimated exploitation activity in the next 30 days; percentile 98.21 (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.

Impact Twig processing of static pages can be enabled in the front matter by any administrative user allowed to create or edit pages. As the Twig processor runs unsandboxed, this behavior can be used to gain arbitrary code execution and elevate privileges on the instance. Patches The issue was addressed by preventing dangerous functions from being called in Twig templates. A configuration option has been added to manually allow arbitrary PHP functions (system.twig.safefunctions) and filters (system.twig.safefilters). Futures major versions of Grav may disable this functionality by default. Workarounds Blocking access to the /admin path from untrusted sources will reduce the probability of exploitation. References - https://portswigger.net/research/server-side-template-injection - https://blog.sonarsource.com/grav-cms-code-execution-vulnerabilities For more information If you have any questions or comments about this advisory, you can contact: - The original reporters, by sending an…

Published by the source

16 Apr 2021, 19:53 UTC

Last modified by the source

29 Jan 2023, 05:02 UTC

Source last checked

26 Oct 2026, 14:00 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-g8r4-p96j-xfxc

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# Patch Next advisory brief: CVE-2021-29440

Advisory: Grav's Twig processing allowing dangerous PHP functions by default
IDs: CVE-2021-29440, GHSA-g8r4-p96j-xfxc
Record: https://patchnext.com/advisories/cve-2021-29440 (revision 1, source checked 26 Oct 2026, 14:00 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: getgrav/grav 1.7.11. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist getgrav/grav: affected <= 1.7.10; fixed in 1.7.11

## 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-g8r4-p96j-xfxc (GitHub-reviewed advisory GHSA-g8r4-p96j-xfxc lists affected ranges: Packagist getgrav/grav >=0 <=1.7.10)

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