PatchSiren cyber security CVE debrief
CVE-2026-58657 Grav CVE debrief
CVE-2026-58657 is a stored CSS injection vulnerability in Grav before 2.0.0. The vulnerability exists 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 enables UI redress/overlay and content-manipulation attacks.
- Vendor
- Grav
- Product
- Unknown
- CVSS
- MEDIUM 4.8
- CISA KEV
- Not listed in stored evidence
- Original CVE published
- 2026-07-08
- Original CVE updated
- 2026-07-08
- Advisory published
- 2026-07-08
- Advisory updated
- 2026-07-08
Who should care
Users of Grav versions before 2.0.0 should be aware of this vulnerability and take steps to mitigate it. This includes content editors and administrators who have the ability to edit page Markdown. They should review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.
Technical summary
The vulnerability exists in the Markdown image resize() media action in Grav before 2.0.0. A lower-privileged content editor can store a crafted image URL with semicolon-delimited CSS declarations in the resize parameters. When a higher-privileged reviewer/admin views the page or preview, the CSS declarations are rendered into the final <img style=...> attribute. This enables UI redress/overlay and content-manipulation attacks. The vulnerability can be exploited without JavaScript execution.
Defensive priority
Medium
Recommended defensive actions
- Update Grav to version 2.0.0 or later
- Restrict editing of page Markdown to trusted users
- Monitor for suspicious activity on your Grav site
- Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up.
- Review compensating controls for exposed systems while remediation is scheduled and verified.
- Check relevant monitoring, detection, and logs for exposed assets that need extra review.
- Track exceptions, retest remediated assets, and close the item only after evidence is documented.
Evidence notes
The CVE record was published on 2026-07-08T14:17:20.440Z and has not been modified since then. The NVD entry is currently Deferred. There is limited information available about the vulnerability, and defenders should verify the affected scope and severity with the vendor. The vulnerability exists in the Markdown image resize() media action in Grav before 2.0.0. A lower-privileged content editor can store a crafted image URL with semicolon-delimited CSS declarations in the resize parameters. When a higher-privileged reviewer/admin views the page or preview, the CSS declarations are rendered into the final <img style=...> attribute. This enables UI redress/overlay and content-manipulation attacks. Defenders should review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.
Official resources
AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-08T14:17:20.440Z and has not been modified since then. The NVD entry is currently Deferred.