CVE-2026-102997: pypdf DoS — Fix

Description

pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF containing a partially malformed /FlateDecode stream with padded data can force pypdf/filters.py to use inefficient byte-by-byte decompression while the earlier recovery counter fails to advance for bytes that successfully decode, causing long runtimes and application unavailability. This is a residual issue after the malformed FlateDecode recovery fix. This issue is fixed in version 6.18.1.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0035

Probability of exploitation

0.26%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-400 Uncontrolled Resource Consumption

CWE-407 CWE-407

Affected Products

Vendor	Product	Versions
pypdf_project	pypdf	< 6.18.1

References

Advisories & Patches

https://github.com/py-pdf/pypdf/commit/d9d38cf99b115deb562d3b68f36c33027bc04f79 https://github.com/py-pdf/pypdf/pull/4073 https://github.com/py-pdf/pypdf/security/advisories/GHSA-jw7q-gvrg-4vj3

Other References

https://github.com/py-pdf/pypdf/releases/tag/6.18.1

Frequently Asked Questions

What is CVE-2026-102997? +

pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF containing a partially malformed /FlateDecode stream with padded data can force pypdf/filters.py to use inefficient byte-by-byte decompression while the earlier recovery counter fails to advance for bytes that successfully decode, causing long runtimes and application unavailability. This is a residual issue after the malformed FlateDecode recovery fix. This issue is fixed in version 6.18.1. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-102997? +

CVE-2026-102997 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0035, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-102997? +

CVE-2026-102997 affects products from pypdf_project, specifically: pypdf. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-102997? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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