# CVE-2026-58657: Grav - Stored CSS Injection via Markdown Image resize() Action

> A lower-privileged editor can inject CSS via Markdown image resize parameters, enabling UI redress attacks against higher-privileged users viewing the page.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 8 Jul 2026
- **Updated:** 8 Oct 2026
- **Also known as:** GHSA-ffmg-hfvg-jhg9

## What is CVE-2026-58657?

CVE-2026-58657 is a medium-severity cross-site scripting vulnerability in Grav, published on 8 Jul 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.

### 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.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-58657?

2 open source packages ship an affected version, including getgrav/grav.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `getgrav/grav` | Packagist | From 2.0.0-rc.9 | 2.0.0 |
| `getgrav/grav` | Packagist | From 2.0.0-rc.9 | 2.0.0 |

## How do I fix CVE-2026-58657?

Upgrade getgrav/grav to 2.0.0 or later.

## Is CVE-2026-58657 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-58657 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-58657 and fix it if it is affected.

What it is: CVE-2026-58657 is a medium-severity cross-site scripting vulnerability in Grav, published on 8 Jul 2026. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-58657 exists.

Affected packages and fixed versions:
- getgrav/grav (Packagist): affected from 2.0.0-rc.9; fixed in 2.0.0
- getgrav/grav (Packagist): affected from 2.0.0-rc.9; fixed in 2.0.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-58657/ (Markdown: https://insights.sbomify.com/CVE-2026-58657/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-58657
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-58657
- OSV: https://osv.dev/vulnerability/CVE-2026-58657

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-58657/
Summaries are generated and may contain mistakes; the official description above is the record.