CVE-2026-84311 pypdf: Possible long runtimes/large memory usage when extracting XForm objects
An attacker can cause denial of service via long runtimes and high memory usage by crafting a PDF with reused form XObjects in pypdf.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-84311?
CVE-2026-84311 is a medium-severity denial of service vulnerability in Pypdf Project Pypdf, published on 1 Sep 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
pypdf is a free and open-source pure-python PDF library. Prior to 6.16.1, an attacker can craft a PDF that causes pypdf/_page.py PageObject._extract_text and PageObject.extract_xform_text to traverse a directed acyclic graph of reused form XObjects in which each form invokes a child multiple times, creating exponentially many traversal paths and causing long runtimes and large memory consumption. This issue is fixed in version 6.16.1.
Weakness: CWE-834
Which versions are affected by CVE-2026-84311?
3 open source packages ship an affected version, including pypdf. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
pypdf PyPI | All versions | 6.16.1 |
pypdf PyPI | All versions | 6.16.1 |
pypdf PyPI | All versions | 6.16.1 |
Products include Pypdf Project Pypdf.
How do I fix CVE-2026-84311?
Upgrade pypdf to 6.16.1 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-84311 being exploited?
There is no known exploitation of CVE-2026-84311 in the wild and no public exploit code.
Other vulnerabilities in Pypdf Project Pypdf
- CVE-2026-102993 pypdf: Possible large memory usage when retrieving Roman page labels
- CVE-2026-102994 pypdf: Possible long runtimes/large memory usage when parsing indirect objects
- CVE-2026-102995 pypdf: Possible large memory usage for large /ToUnicode streams (Follow-up 2)
- CVE-2026-102996 pypdf: Possible large memory usage when parsing font data
- CVE-2026-102997 pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)
Sources
Also known as DEBIAN-CVE-2026-84311, ECHO-7b2c-9b22-8657, GHSA-763m-79hh-57f2, MINI-7f8w-qc4x-h7mc, MINI-8v44-p828-ph7h, MINI-cg65-v279-w6c9 and 10 more.