XSS in Grav

CVE-2026-58657

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.

Vulnerability class: XSS (Cross-Site Scripting)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 4.8 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.004 (29.0th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 29th percentile — 29.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-58657: held from 0.004 to 0.004.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000

Affected products

  • Grav — versions 2.0.0-rc.9, 2.0.0

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-58657?
CVE-2026-58657 is a medium-severity vulnerability in Grav, classified under Cross-site Scripting. CVSS score: 4.8/10. Published 2026-07-08.
How severe is CVE-2026-58657?
Medium severity. CVSS v3 base score is 4.8 out of 10.