Grav: Stored CSS injection via Markdown image ?style=… reaches MediaObjectTrait::style() — incomplete patch of GHSA-r7fx-8g49-7hhr

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.8 · CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2026-55890: 0.50% estimated exploitation activity in the next 30 days; percentile 43.09 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The fix for GHSA-r7fx-8g49-7hhr / CVE-2026-42841 (Stored XSS via Markdown media attribute() action) is incomplete. The maintainer patched MediaObjectTrait::attribute() to deny dangerous attribute names (event handlers, style, xmlns, srcdoc, formaction) but the sibling MediaObjectTrait::style() method is reachable through the same Markdown excerpt-action pipeline and writes editor-controlled strings straight into the rendered <img style="…" attribute with no sanitization. Any user with admin.pages permission (e.g. an editor) can save Markdown like: which renders to a stored-CSS payload that any higher-privileged viewer (administrator, super-admin, reviewer) loads in their authenticated session. Same trust boundary, same victim, same attacker, same Markdown input vector as the patched GHSA-r7fx-8g49-7hhr issue — the fix simply patched the attribute() entry point and missed the style() sibling. Affected versions Vulnerable at HEAD across every currently-shipping branch (verified…

Published by the source

18 Jun 2026, 14:49 UTC

Last modified by the source

18 Jun 2026, 14:49 UTC

Source last checked

26 Oct 2026, 14:49 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-pmf8-g7c8-7v54

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# Patch Next advisory brief: CVE-2026-55890

Advisory: Grav: Stored CSS injection via Markdown image ?style=… reaches MediaObjectTrait::style() — incomplete patch of GHSA-r7fx-8g49-7hhr
IDs: CVE-2026-55890, GHSA-pmf8-g7c8-7v54
Record: https://patchnext.com/advisories/cve-2026-55890 (revision 1, source checked 26 Oct 2026, 14:49 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: getgrav/grav 2.0.0-rc.9. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist getgrav/grav: affected <= 2.0.0-rc.8; fixed in 2.0.0-rc.9

## Suggested inspection (read-only)
- Packagist getgrav/grav: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on getgrav/grav.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-pmf8-g7c8-7v54 (GitHub-reviewed advisory GHSA-pmf8-g7c8-7v54 lists affected ranges: Packagist getgrav/grav >=0 <=2.0.0-rc.8)

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