CVE-2023-36464 is a medium-severity vulnerability affecting the pypdf and pypdf2 libraries, which are open-source, pure-Python PDF libraries. In affected versions, an attacker can craft a malicious PDF that leads to an infinite loop when the `__parse_content_stream` method is executed. This situation may occur, for instance, if a user attempts to extract text from such a PDF. The issue was introduced in pull request #969 and was resolved in pull request #1828. Organizations using these libraries must take immediate action.
The CVSS score of this vulnerability is 6.2, indicating a medium severity level. This score reflects an attack vector of local, low attack complexity, and no privileges or user interaction required, but it can lead to high availability impact. Risk to organizations includes potential service disruptions due to an infinite loop being triggered in the affected libraries.
Organizations should prioritize patching immediately. Users are advised to upgrade to the latest version of pypdf or pypdf2 to mitigate this risk. For those unable to upgrade, a temporary workaround is to modify the line in `pypdf/generic/_data_structures.py` from `while peek not in (b"\r", b"\n")` to `while peek not in (b"\r", b"\n", b"")`.
The vulnerability has been publicly disclosed, and while there are no known exploits, the potential for abuse remains concerning. Users should monitor their systems closely and apply the necessary updates without delay.
Vulnerability Details
This vulnerability allows an attacker to create a PDF that causes an infinite loop during content parsing. The issue is linked to `pypdf` and `pypdf2` versions prior to 3.9.0 and 2.2.0 respectively. The vulnerability classification is CWE-835, which refers to infinite loop issues.
Technical Analysis
The root cause of this vulnerability lies in the content parsing logic of the affected libraries. When a PDF is processed, if a specific condition is met, it can lead to an infinite loop due to improper handling of certain content structures. Due to the nature of the libraries being local, the attack vector requires that an attacker have access to a system where the vulnerable library is installed.
The attack complexity is low, as it does not require any special privileges or user interaction. However, the impact on availability can be significant, leading to service outages if the infinite loop is triggered.
Risk & Impact Analysis
Real-world deployment risk is moderate, as the infinite loop can cause denial of service conditions in applications relying on these libraries. Organizations should assess their exposure to this vulnerability based on their use of pypdf and pypdf2. The blast radius potential is limited to systems utilizing these libraries, but the impact could be severe, resulting in downtime.
Given the CVSS score of 6.2, organizations should address this issue in their priority patch cycle. The availability impact is rated high, making it a critical concern for operational continuity.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The affected versions of the pypdf library are all versions prior to 3.9.0. For the pypdf2 library, the affected versions are from 2.2.0 and onwards. Users should ensure they are using the latest versions to avoid this vulnerability.
Mitigation & Remediation
Organizations should prioritize upgrading to the latest version of pypdf or pypdf2 to eliminate this vulnerability. If immediate upgrading is not feasible, users can modify the line in `pypdf/generic/_data_structures.py` to prevent the infinite loop, as mentioned earlier. It is also advisable to implement security testing practices to identify similar vulnerabilities in other libraries.
For more information on best practices for security testing, organizations can refer to the penetration testing methodology guide.
Detection Guidance
To effectively monitor for exploitation attempts, organizations should look out for log indicators related to PDF processing failures and any unusual behavior when handling PDFs. Monitoring network traffic for known patterns of malicious PDF usage can also be beneficial.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2023-36464 lies in its representation of a common flaw in PDF processing libraries, where improper handling can lead to denial of service conditions. Security teams should note this pattern and enhance their security assessments of third-party libraries to prevent similar vulnerabilities.
Continued vigilance and proactive security measures are essential as libraries like pypdf and pypdf2 are widely used. For insights into managing security vulnerabilities in your applications, the vulnerability management program can provide a structured approach to address such risks.
Utilizing comprehensive security assessments and leveraging resources like the application security assessment can also help organizations identify and remediate vulnerabilities effectively.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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