CVE-2026-22691 is a vulnerability affecting the pypdf library, an open-source pure-Python PDF library. This vulnerability allows attackers to craft PDFs that lead to extended processing times when handling malformed 'startxref' entries. The issue, present in versions prior to 6.6.0, particularly impacts the non-strict reading mode. Organizations using affected versions should be aware of the potential performance implications.
The CVSS score for this vulnerability is 2.7, which categorizes it as low severity. Although the risk is relatively low, it is crucial for organizations to assess their exposure to this vulnerability as it could lead to denial-of-service conditions due to excessive runtimes when processing certain PDF files.
Currently, there are no known exploits or public proof-of-concept (PoC) code available for CVE-2026-22691. However, organizations should still take this vulnerability seriously and prioritize upgrading to the patched version 6.6.0 immediately to avoid any potential issues stemming from this vulnerability.
Organizations should prioritize patching immediately.
Vulnerability Details
The official description of CVE-2026-22691 states that prior to version 6.6.0, pypdf has possible long runtimes for malformed startxref entries. Attackers may leverage this vulnerability by crafting PDFs that lead to long runtimes for invalid startxref entries. The issue has been patched in version 6.6.0.
The vulnerability has been classified under CWE-400 (Uncontrolled Resource Consumption) and CWE-1333 (Excessive Resource Consumption).
The CVSS 3.1 base score is 5.3, indicating a medium severity level, while the CVSS 4.0 base score is 2.7, indicating low severity. The attack vector is network-based, with low complexity and no privileges required.
Technical Analysis
The root cause of this vulnerability lies in the handling of malformed startxref entries within PDF files. When the library attempts to rebuild the cross-reference table, it can encounter issues, especially with files containing excessive whitespace characters. The attack vector is network-based, meaning an attacker can exploit this vulnerability remotely by sending a specially crafted PDF file.
The attack complexity is low, as no special conditions or privileges are required to exploit this vulnerability. User interaction is not necessary, allowing for easy exploitation by an attacker. The availability impact is categorized as low, as it may lead to denial-of-service conditions due to prolonged runtimes during PDF processing.
Risk & Impact Analysis
Organizations using the pypdf library should be aware of the risk presented by CVE-2026-22691. The potential for denial-of-service conditions due to excessive runtimes could disrupt normal operations, particularly in systems that rely heavily on PDF processing. Given that the attack vector is network-based, the vulnerability can be exploited remotely, increasing the blast radius for affected organizations.
The low CVSS score suggests that while the risk is manageable, organizations should not overlook the importance of addressing this vulnerability promptly. Failure to patch could lead to performance issues, particularly for applications that handle large volumes of PDF files.
Organizations should schedule remediation and prioritize this in their patch management processes.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The affected version is any prior to 6.6.0 of the pypdf library. Organizations should upgrade to version 6.6.0 or later to mitigate the risk associated with this vulnerability.
Mitigation & Remediation
To remediate CVE-2026-22691, organizations should upgrade to pypdf version 6.6.0 or later. This version addresses the vulnerability and improves the handling of malformed PDF files.
Additionally, organizations should implement configuration hardening measures to limit the exposure of their systems to potential malformed PDF files. Monitoring for unusual behavior during PDF processing may also help in identifying potential abuse of this vulnerability.
For more comprehensive security measures, organizations may consider engaging in penetration testing to validate their defenses against such vulnerabilities.
Detection Guidance
Organizations should monitor logs for indicators of unusual PDF processing that may suggest exploitation of this vulnerability. Specific indicators may include long processing times for certain PDF files or errors related to malformed entries in the cross-reference tables.
Behavioral anomalies during regular PDF processing workflows should be investigated to determine if they are indicative of an attempted exploitation of CVE-2026-22691.
AppSecure Threat Intelligence Insight
CVE-2026-22691 highlights the importance of robust input validation and handling in libraries that process complex file formats like PDF. Organizations should consider reviewing their security practices surrounding third-party libraries and ensure that they are regularly updated.
This vulnerability serves as a reminder that even lower-severity vulnerabilities can have operational impacts if left unaddressed. Organizations should maintain a proactive approach to security by staying informed about vulnerabilities in the libraries they utilize.
For further insights into security best practices, organizations may benefit from exploring resources on penetration testing methodology, vulnerability management program design, and web application penetration testing to strengthen their defenses.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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