CVE-2023-50262: Dompdf possible DoS caused by infinite recursion when parsing SVG images
First published: Wed Dec 13 2023(Updated: )
### Summary When parsing SVG images Dompdf performs an initial validation to ensure that paths within the SVG are allowed. One of the validations is that the [SVG document does not reference itself](https://github.com/dompdf/dompdf/blob/v2.0.3/src/Image/Cache.php#L136-L153). However, a recursive chained using two or more SVG documents is not correctly validated. Depending on the system configuration and attack pattern this could exhaust the memory available to the executing process and/or to the server itself. ### Details php-svg-lib, when run in isolation, does not support SVG references for `image` elements. An SVG document can, however, be referenced and Dompdf will run that reference through the same validation. Dompdf currently includes validation to prevent self-referential `image` references, but a chained reference is not checked. A malicious actor may thus trigger infinite recursion in the validation process by chaining references between two or more SVG images. ### PoC This following sources can be used to bypass validation provided by Dompdf: recurse.html ``` <img src="one.svg"> ``` one.svg ``` <svg width="200" height="200" xmlns="http://www.w3.org/2000/svg"> <image href="two.svg" /> </svg> ``` two.svg ``` <svg width="200" height="200" xmlns="http://www.w3.org/2000/svg"> <image href="one.svg" /> </svg> ``` ### Impact When Dompdf parses the above payload, it will crash due after exceeding the allowed execution time or memory usage. An attacker sending multiple request to a system can potentially cause resource exhaustion to the point that the system is unable to handle incoming request.
Credit: security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| composer/dompdf/dompdf | <2.0.4 | 2.0.4 |
| Dompdf | <=2.0.3 |
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Reference Links
- https://github.com/dompdf/dompdf/security/advisories/GHSA-3qx2-6f78-w2j2
- https://nvd.nist.gov/vuln/detail/CVE-2023-50262
- https://github.com/dompdf/dompdf/commit/41cbac16f3cf56affa49f06e8dae66d0eac2b593
- https://github.com/dompdf/dompdf/blob/v2.0.3/src/Image/Cache.php#L136-L153
- https://github.com/FriendsOfPHP/security-advisories/blob/master/dompdf/dompdf/CVE-2023-50262.yaml
- https://github.com/advisories/GHSA-3qx2-6f78-w2j2 (Advisory)
Frequently Asked Questions
What is the severity of CVE-2023-50262?
CVE-2023-50262 has been classified as a medium-severity vulnerability.
How do I fix CVE-2023-50262?
To fix CVE-2023-50262, upgrade Dompdf to version 2.0.4 or later.
What is the main risk associated with CVE-2023-50262?
The main risk associated with CVE-2023-50262 is potential XML External Entity (XXE) injection which can lead to information disclosure.
Which versions of Dompdf are affected by CVE-2023-50262?
Dompdf versions prior to 2.0.4 are affected by CVE-2023-50262.
Is it safe to use SVG images with affected versions of Dompdf?
Using SVG images with affected versions of Dompdf can be risky due to the self-referential path validation issue.
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