Vulnerability · Published Jul 8, 2026 · Assigned by VulnCheck
CVE-2026-58657Grav - Stored CSS Injection via Markdown Image resize() Action
Medium 4.8
In plain English
A medium-severity cross-site scripting in Grav from Grav. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Packagist | getgrav/grav | 2.0.0 | GHSA-ffmg-hfvg-jhg9 |
Affected products (as reported)
Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
References
- GitHub Security Advisory (GHSA-ffmg-hfvg-jhg9) vendor-advisory
- https://github.com/getgrav/grav/commit/6582166173bb8eb5869d96aea384e0e73777c94c patch
- https://github.com/getgrav/grav/commit/e03d29aa0d3ece16d73c1ffccfa78df8bf5f28b8 patch
- VulnCheck Advisory: Grav - Stored CSS Injection via Markdown Image resize() Action third-party-advisory