pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up) (CVE-2026-102997) | HOL Guard CVE

High · CVSS 8.7CVE-2026-102997

pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)

Answer in brief

CVE-2026-102997 records a High severity (CVSS 8.7) vulnerability in pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up). The current sources do not mark it as known exploited. The current feed maps py-pdf/pypdf (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 30, 2026Updated Sep 30, 2026Source checked Sep 30, 2026First seen by HOL Sep 30, 2026Material review Sep 30, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.7
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps py-pdf/pypdf (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
py-pdf/pypdfgeneric	<6.18.1	6.18.1

Recommended response

Check inventory. Check lockfiles and deployed manifests for py-pdf/pypdf.
Review the reported fix. Update py-pdf/pypdf to 6.18.1 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 30, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 30, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 30, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.