Is CVE-2026-102997 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-102997 being exploited in the wild.

How severe is CVE-2026-102997?

High severity, with a CVSS score of 4, published 30 September 2026.

Which products and versions are affected?

Py-Pdf Pypdf before 6.18.1; pypdf (PyPI) < 6.18.1, ECOSYSTEM:introduced=0,fixed=6.18.1.

Is there a fix for CVE-2026-102997?

Yes. pypdf (PyPI): upgrade to 6.18.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-102997 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-102997?

Check whether you run Py-Pdf Pypdf or pypdf (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-102997: pypdf denial of service in FlateDecode decompression

Q: Is there a fix for CVE-2026-102997?

Yes. pypdf (PyPI): upgrade to 6.18.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Q: How is CVE-2026-102997 attacked?

It is attacked over the network, in a software library.

Q: Am I affected by CVE-2026-102997?

Check whether you run Py-Pdf Pypdf or pypdf (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-102997 · Severity: high · CVSS 4 · Published 2026-09-30

pypdf is a Python library for reading and manipulating PDF files. A specially crafted PDF with a malformed compression stream can force the library into slow byte-by-byte decompression, consuming excessive CPU and causing application hangs or unavailability. The vulnerability affects versions before 6.18.1.

Technologies: Py-Pdf Pypdf, pypdf (PyPI). Vendors: Py-Pdf, PyPI.

Quick answers

Is CVE-2026-102997 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-102997 being exploited in the wild.
How severe is CVE-2026-102997?: High severity, with a CVSS score of 4, published 30 September 2026.
Which products and versions are affected?: Py-Pdf Pypdf before 6.18.1; pypdf (PyPI) < 6.18.1, ECOSYSTEM:introduced=0,fixed=6.18.1.
Is there a fix for CVE-2026-102997?: Yes. pypdf (PyPI): upgrade to 6.18.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-102997 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-102997?: Check whether you run Py-Pdf Pypdf or pypdf (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

pypdf (PyPI): upgrade to 6.18.1 or later
```
pip install "pypdf>=6.18.1"
```

Technical details

A partially malformed /FlateDecode stream with padded data bypasses the recovery counter mechanism in pypdf/filters.py, triggering inefficient byte-by-byte decompression instead of the normal fast path. The counter fails to advance for bytes that successfully decode, allowing an attacker to craft a malicious PDF that triggers long runtimes. This is fixed in version 6.18.1 by further restricting when the FlateDecode recovery mechanism is invoked.

Affected products

py-pdf pypdf before 6.18.1

Identifiers

CVE-2026-102997
GHSA-jw7q-gvrg-4vj3
PYSEC-2026-4156

Timeline

2026-09-30: disclosed
2026-09-11: patched: Fix merged in version 6.18.1

References

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