Overview
CVE-2025-66019 describes a memory exhaustion vulnerability affecting pypdf, a popular Python library for PDF manipulation. Prior to version 6.4.0, a specially crafted PDF file could trigger excessive memory usage when parsing its content stream using the LZWDecode filter. This vulnerability could lead to denial-of-service (DoS) conditions if exploited.
Technical Details
The vulnerability lies within the LZWDecode filter implementation within pypdf. An attacker can create a PDF document with a malicious content stream that, when processed by pypdf versions before 6.4.0, leads to the allocation of up to 1GB of memory per stream. This occurs during the decompression process of the LZW encoded data. By embedding several malicious streams, an attacker can quickly exhaust available memory, causing the application using pypdf to crash or become unresponsive.
CVSS Analysis
Currently, a CVSS score has not been assigned for CVE-2025-66019. However, the potential for denial-of-service (DoS) suggests a moderate to high severity, depending on the context of pypdf usage. The CVSS score is “N/A” as of this writing because the assessment process may be ongoing.
Possible Impact
Successful exploitation of CVE-2025-66019 can result in:
- Denial of Service (DoS): Applications using vulnerable pypdf versions could crash or become unresponsive due to excessive memory consumption.
- Resource Exhaustion: Servers or systems processing malicious PDFs could experience high CPU and memory usage.
- Potential for Further Exploitation: In some cases, a DoS vulnerability can be a stepping stone for more severe attacks.
Mitigation and Patch Steps
The vulnerability has been addressed in pypdf version 6.4.0. To mitigate the risk, users are strongly advised to upgrade to version 6.4.0 or later. You can upgrade pypdf using pip:
pip install --upgrade pypdfIf upgrading is not immediately feasible, consider implementing input validation to filter potentially malicious PDF files. However, upgrading remains the most effective solution.
