CVE-2026-84311 py-pdf CVE debrief

Who should care

Defenders responsible for systems and applications using the pypdf library should assess exposure and prioritize updating to version 6.16.1 or later. Defenders should review and update affected systems and applications to prevent potential denial-of-service attacks. The vulnerability affects operators, platforms, and security teams that use the pypdf library, and they should verify and update affected systems and applications to prevent potential attacks.

Why it matters

CVE-2026-84311 is a vulnerability in the pypdf library that can cause long runtimes and large memory consumption when processing a specially crafted PDF. Defenders should prioritize updating to version 6.16.1 or later to prevent potential denial-of-service attacks.

• Potential denial-of-service attacks due to long runtimes and large memory consumption
• Need to verify and update affected systems and applications to prevent potential attacks

Technical summary

The pypdf library is vulnerable to a denial-of-service attack when processing a specially crafted PDF. The issue is caused by a directed acyclic graph of reused form XObjects in a PDF, which can create exponentially many traversal paths and cause long runtimes and large memory consumption. This vulnerability affects systems and applications using the pypdf library, and defenders should prioritize updating to version 6.16.1 or later to prevent potential denial-of-service attacks. The vulnerability can be exploited by an attacker to cause long runtimes and large memory consumption.

Defensive priority

Defenders should prioritize updating to version 6.16.1 or later to prevent potential denial-of-service attacks.

Recommended defensive actions

• Update to pypdf version 6.16.1 or later
• Review and update affected systems and applications
• Monitor for potential denial-of-service attacks
• Verify and update affected systems and applications to prevent potential attacks
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The vulnerability is caused by a directed acyclic graph of reused form XObjects in a PDF, which can create exponentially many traversal paths and cause long runtimes and large memory consumption. This issue is fixed in version 6.16.1. The vulnerability affects systems and applications using the pypdf library, and defenders should verify and update affected systems and applications to prevent potential denial-of-service attacks. The CVE record was published on 2026-09-01T21:18:46.887Z and has not been modified since then.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.