CVE-2025-55197Public exploitNetwork attack vector

Service interruption via unbounded FlateDecode expansion

Published Aug 13, 2025 · Updated Aug 14, 2025

Resource exhaustion in py-pdf pypdf before 6.0.0 allows remote attackers to interrupt a consuming service with a crafted PDF. The pypdf.filters.decompress path passes each FlateDecode layer to zlib without bounding decompressed output, so stacked filters expand a small stream to enormous size. Exploitation requires an application to read a malicious cross-reference stream or explicitly access another affected content stream, exhausting RAM in that process.

CVSS severityUnavailable
Unscored
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in py-pdf pypdf before 6.0.0 allows remote attackers to interrupt a consuming service with a crafted PDF. The pypdf.filters.decompress path passes each FlateDecode layer to zlib without bounding decompressed output, so stacked filters expand a small stream to enormous size. Exploitation requires an application to read a malicious cross-reference stream or explicitly access another affected content stream, exhausting RAM in that process.

The record

CVE
CVE-2025-55197
Published
Aug 13, 2025
Updated
Aug 14, 2025
Vendor
py-pdf
Product
pypdf
Classifications
CWE-770, CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 13, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 14, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 6.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

py-pdf · pypdfversion=< 6.0.0

Published CVSS scores

6.6GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
CWE-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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