CVE-2026-33123: pypdf is a free and open-source pure-python PDF library

Q: How do I fix CVE-2026-33123?

pypdf: upgrade to 6.9.1. Exact commands for each OS are on this page.

Q: Is CVE-2026-33123 being exploited?

CVE-2026-33123 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-33123 affect?

CVE-2026-33123 affects pypdf. Severity is medium (CVSS 6.5). pypdf is a free and open-source pure-python PDF library. Versions prior to 6.9.1 allow an attacker to craft a malicious PDF which leads to long runtimes and/or large memory usage. Exploitation requires accessing an array-based stream with m

Q: How urgent is CVE-2026-33123?

Priority 30/100. No elevated risk signals yet.

Routine

MEDIUM 6.5UPGRADE

CVE-2026-33123 is a medium-severity flaw (CVSS 6.5) affecting pypdf. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

pypdf is a free and open-source pure-python PDF library. Versions prior to 6.9.1 allow an attacker to craft a malicious PDF which leads to long runtimes and/or large memory usage. Exploitation requires accessing an array-based stream with many entries. This issue has been fixed in version 6.9.1.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.4% (top 71%)
CISA exploited list	No
Weakness	CWE-400, CWE-407
Published	2026-03-20
Last modified	2026-11-02

Publisher (CNA): GitHub, Inc. · Vendor: py-pdf

Last updated 2026-11-02 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-20 10:16 UTCPublished CVE record published
2026-11-02 16:06 UTCUpdated Record last modified

py-pdf pypdf UPGRADE

Affected: < 6.9.1

Fixed in: 6.9.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy pypdf || rpm -q pypdf || pypdf --version

2. UPGRADE to 6.9.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade pypdf

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade pypdf

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-33123?

pypdf: upgrade to 6.9.1. Exact commands for each OS are on this page.

Is CVE-2026-33123 being exploited?

CVE-2026-33123 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-33123 affect?

CVE-2026-33123 affects pypdf. Severity is medium (CVSS 6.5). pypdf is a free and open-source pure-python PDF library. Versions prior to 6.9.1 allow an attacker to craft a malicious PDF which leads to long runtimes and/or large memory usage. Exploitation requires accessing an array-based stream with m

How urgent is CVE-2026-33123?

Priority 30/100. No elevated risk signals yet.

Software pages

Python vulnerabilities

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References

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