Grav up to 2.0.0-rc.9 Media Action processMediaActions resize injection

Summaryinfo

A vulnerability marked as critical has been reported in Grav up to 2.0.0-rc.9. This impacts the function Excerpts::processMediaActions of the component Media Action Handler. This manipulation of the argument resize causes injection. This vulnerability is handled as CVE-2026-58657. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in Grav up to 2.0.0-rc.9. It has been declared as critical. Affected by this vulnerability is the function Excerpts::processMediaActions of the component Media Action Handler. The manipulation of the argument resize with an unknown input leads to a injection vulnerability. The CWE definition for the vulnerability is CWE-74. The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

Grav before 2.0.0 (affected through 2.0.0-rc.9 and the 2.0 branch) contains a stored CSS injection vulnerability in the Markdown image resize() media action. Prior media hardening rejects direct ?style= payloads and unsafe attribute() fallbacks, but the resize() action in Excerpts::processMediaActions() writes caller-controlled values directly into the image's styleAttributes. A lower-privileged content editor who can edit page Markdown can store a crafted image URL with semicolon-delimited CSS declarations in the resize parameters, which are rendered into the final <img style=...> attribute when a higher-privileged reviewer/admin views the page or preview. This does not require JavaScript execution but enables UI redress/overlay and content-manipulation attacks (e.g., a full-viewport fixed overlay). Fixed in 2.0.0.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-58657 since 07/01/2026. The exploitation appears to be easy. The attack can be launched remotely. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1055 according to MITRE ATT&CK.

Upgrading to version 2.0.0 eliminates this vulnerability.

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Productinfo

Name

• Grav

Version

• 2.0.0-rc.0
• 2.0.0-rc.1
• 2.0.0-rc.2
• 2.0.0-rc.3
• 2.0.0-rc.4
• 2.0.0-rc.5
• 2.0.0-rc.6
• 2.0.0-rc.7
• 2.0.0-rc.8
• 2.0.0-rc.9

CPE 2.3info

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CPE 2.2info

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