Getgrav Grav up to 2.0.24 Twig Sandbox process.twig applyTwigContentDefault authentication replay

Summaryinfo

A vulnerability classified as critical has been found in Getgrav Grav up to 2.0.24. This affects the function Security::applyTwigContentDefault of the file process.twig of the component Twig Sandbox. This manipulation causes authentication replay. This vulnerability is handled as CVE-2026-100671. The attack can be initiated remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Getgrav Grav up to 2.0.24. It has been declared as critical. Affected by this vulnerability is the function Security::applyTwigContentDefault of the file process.twig of the component Twig Sandbox. The manipulation with an unknown input leads to a authentication replay vulnerability. The CWE definition for the vulnerability is CWE-294. A capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes). As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

Grav is a flat-file CMS. In versions 2.0.19 through 2.0.24 — and in 2.0.0 through 2.0.18 and 1.7.x only where content Twig has been explicitly enabled — page content authored by a user holding only page-write permission is rendered through a Twig sandbox that allowlists get_cookie(), which returns any cookie sent with the current request, including the visitor's session cookie. Because the read occurs server-side via filter_input(INPUT_COOKIE, ...), the HttpOnly, Secure and SameSite attributes offer no protection. Grav then stores the finished post-Twig output in a page-content cache keyed only on page identity and the configuration checksum, with no session, user or request dimension and no bypass for authenticated visitors. A page published by a page-write user can therefore capture the session identifier of the next administrator who views it, after which the cached output serves that identifier to unauthenticated visitors, who can replay the cookie to authenticate as that administrator. Since 2.0.19, security.twig_content.process_enabled defaults to true and Security::applyTwigContentDefault() derives each page's process.twig flag from that gate, so content Twig runs on every page with no frontmatter or operator action. Fixed in 2.0.25; 1.7.x is outside the backport scope.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-100671 since 09/26/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1040 according to MITRE ATT&CK.

Upgrading to version 2.0.25 eliminates this vulnerability.

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Productinfo

Vendor

• Getgrav

Name

• Grav

Version

• 2.0.0
• 2.0.1
• 2.0.2
• 2.0.3
• 2.0.4
• 2.0.5
• 2.0.6
• 2.0.7
• 2.0.8
• 2.0.9
• 2.0.10
• 2.0.11
• 2.0.12
• 2.0.13
• 2.0.14
• 2.0.15
• 2.0.16
• 2.0.17
• 2.0.18
• 2.0.19
• 2.0.20
• 2.0.21
• 2.0.22
• 2.0.23
• 2.0.24

Website

• Product: https://github.com/getgrav/grav/

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