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How the CVE Works:
The vulnerability CVE-2025-45424 is triggered when pypdf parses a maliciously crafted PDF file. Specifically, the exploit occurs during the processing of a page’s content stream that contains an inline image using the DCTDecode filter. If this inline image data is crafted to lack a required End-of-File (EOF) marker, the PDF parser enters an infinite loop while attempting to read the image data. The parser’s logic fails to properly handle the missing termination condition, causing it to continuously search for an EOF that does not exist, consuming excessive CPU resources and rendering the application unresponsive. This denial-of-service condition can be exploited by an attacker simply by convincing a user to process the malicious PDF.
Platform: pypdf
Version: <6.1.3
Vulnerability: Infinite Loop
Severity: Moderate
date: 2025-10-22
Prediction: Patch available
What Undercode Say:
`cat malicious.pdf | python3 -m pypdf` This command may hang
`strings malicious.pdf | grep -i “/DCTDecode”` Check for the exploit filter
How Exploit:
An attacker crafts a PDF containing an inline image with a DCTDecode filter that is missing the necessary EOF marker. When this PDF is processed by a vulnerable version of pypdf, the parsing function for the content stream does not correctly handle the malformed image data, leading to an infinite loop and denial of service.
Protection from this CVE:
Upgrade pypdf to version 6.1.3. If an immediate upgrade is not possible, manually apply the code changes from pull request 3501 to the pypdf codebase to implement the necessary checks for the EOF condition.
Impact:
A successful exploit causes a denial of service by putting the Python process into an infinite loop, consuming 100% of a CPU core and making the application unresponsive until the process is manually terminated.
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Sources:
Reported By: github.com
Extra Source Hub:
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