CVE-2026-58657 Grav - Stored CSS Injection via Markdown Image resize() Action
A lower-privileged editor can inject CSS via Markdown image resize parameters, enabling UI redress attacks against higher-privileged users viewing the page.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-58657?
CVE-2026-58657 is a medium-severity cross-site scripting vulnerability in Grav, published on 8 Jul 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
Official description
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.
Weakness: CWE-79
Which versions are affected by CVE-2026-58657?
2 open source packages ship an affected version, including getgrav/grav.
| Package | Affected | Fixed in |
|---|---|---|
getgrav/grav Packagist | From 2.0.0-rc.9 | 2.0.0 |
getgrav/grav Packagist | From 2.0.0-rc.9 | 2.0.0 |
How do I fix CVE-2026-58657?
Upgrade getgrav/grav to 2.0.0 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-58657 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-58657 exists.
Sources
Also known as GHSA-ffmg-hfvg-jhg9.