CVE-2026-58657

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.

PUBLISHED Reserved 2026-07-01 | Published 2026-07-08 | Updated 2026-07-08 | Assigner VulnCheck

Problem types

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Product status

Credits

DavidCarliez reporter

References

github.com/...v/grav/security/advisories/GHSA-ffmg-hfvg-jhg9 exploit

github.com/...v/grav/security/advisories/GHSA-ffmg-hfvg-jhg9 (GitHub Security Advisory (GHSA-ffmg-hfvg-jhg9)) vendor-advisory

github.com/...ommit/6582166173bb8eb5869d96aea384e0e73777c94c patch

github.com/...ommit/e03d29aa0d3ece16d73c1ffccfa78df8bf5f28b8 patch

www.vulncheck.com/...ection-via-markdown-image-resize-action (VulnCheck Advisory: Grav - Stored CSS Injection via Markdown Image resize() Action) third-party-advisory

cve.org (CVE-2026-58657)

nvd.nist.gov (CVE-2026-58657)

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