# GHSA-7jxj-rpx7-ph2c: Umbraco.Forms CDN may cache sensitive form uploads when processed by ImageSharp

> Unauthenticated users can access sensitive form uploads via CDN cache poisoning when ImageSharp processes requests, requiring a CDN and specific file knowledge.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Jan 2026

## What is GHSA-7jxj-rpx7-ph2c?

GHSA-7jxj-rpx7-ph2c is a vulnerability in Umbraco.Forms, published on 22 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

### Impact
Protected files uploaded through Umbraco Forms may be served to unauthenticated users when a CDN or caching layer is present and ImageSharp processes the request. ImageSharp sets aggressive cache headers by default, which can cause intermediary caches to store and serve files that should require authentication.

### Patches
This issue affects all (supported) versions Umbraco Forms and is patched in 13.9.0, 16.4.0 and 17.1.0.

### Workarounds
Add middleware to set cache headers for form uploads. Place the following code in your `Startup.cs` or `Program.cs` after `app.UseStaticFiles()` and any image processing middleware:

```cs
app.Use(async (context, next) =>
{
    var path = context.Request.Path.Value;

    if (!string.IsNullOrEmpty(path) && path.StartsWith("/media/forms/upload/", StringComparison.OrdinalIgnoreCase))
    {
        context.Response.OnStarting(() =>
        {
            context.Response.Headers["Cache-Control"] = "private, no-store, no-cache, must-revalidate";
            context.Response.Headers["Pragma"] = "no-cache";
            context.Response.Headers["Expires"] = "0";
            return Task.CompletedTask;
        });
    }

    await next();
});
```

Alternatively, configure your CDN to bypass caching for URLs matching `/media/forms/upload/*`.

  Note: The vulnerability requires:
  - A CDN in front of the website
  - An authenticated user having previously requested the image
  - Knowledge of the form GUID, entry GUID, and image filename

  If no CDN is in use, this vulnerability does not apply.

## Which versions are affected by GHSA-7jxj-rpx7-ph2c?

6 open source packages ship an affected version, including Umbraco.Forms.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `Umbraco.Forms` | NuGet | All versions | 13.9.0 |
| `Umbraco.Forms` | NuGet | All versions | 13.9.0 |
| `Umbraco.Forms` | NuGet | From 14.0.0-beta001 | 16.4.0 |
| `Umbraco.Forms` | NuGet | From 14.0.0-beta001 | 16.4.0 |
| `Umbraco.Forms` | NuGet | From 17.0.0-rc1 | 17.1.0 |
| `Umbraco.Forms` | NuGet | From 17.0.0-rc1 | 17.1.0 |

## How do I fix GHSA-7jxj-rpx7-ph2c?

Upgrade Umbraco.Forms to a fixed version for your release line: 13.9.0, 16.4.0 or 17.1.0.

## Is GHSA-7jxj-rpx7-ph2c being exploited?

There is no known exploitation of GHSA-7jxj-rpx7-ph2c in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-7jxj-rpx7-ph2c and fix it if it is affected.

What it is: GHSA-7jxj-rpx7-ph2c is a vulnerability in Umbraco.Forms, published on 22 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of GHSA-7jxj-rpx7-ph2c in the wild and no public exploit code.

Affected packages and fixed versions:
- Umbraco.Forms (NuGet): affected all versions; fixed in 13.9.0
- Umbraco.Forms (NuGet): affected all versions; fixed in 13.9.0
- Umbraco.Forms (NuGet): affected from 14.0.0-beta001; fixed in 16.4.0
- Umbraco.Forms (NuGet): affected from 14.0.0-beta001; fixed in 16.4.0
- Umbraco.Forms (NuGet): affected from 17.0.0-rc1; fixed in 17.1.0
- Umbraco.Forms (NuGet): affected from 17.0.0-rc1; fixed in 17.1.0

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/GHSA-7jxj-rpx7-ph2c/ (Markdown: https://insights.sbomify.com/GHSA-7jxj-rpx7-ph2c/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-7jxj-rpx7-ph2c

---
From sbomify Insights: https://insights.sbomify.com/GHSA-7jxj-rpx7-ph2c/
Summaries are generated and may contain mistakes; the official description above is the record.