CVE-2026-27888Network attack vector

Service interruption via unbounded XFA decompression

Published Feb 26, 2026 · Updated Feb 26, 2026

Uncontrolled resource consumption in pypdf before 6.7.3 allows remote attackers to exhaust RAM through a crafted PDF XFA stream. The xfa property in pypdf/_doc_common.py passes compressed XFA field data directly to zlib.decompress without an output-size limit. An application must access a reader or writer's xfa property on a PDF whose corresponding stream uses /FlateDecode, after which decompression can exhaust process memory and interrupt service.

CVSS severity7.5
High
EPSS probability0.35%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in pypdf before 6.7.3 allows remote attackers to exhaust RAM through a crafted PDF XFA stream. The xfa property in pypdf/_doc_common.py passes compressed XFA field data directly to zlib.decompress without an output-size limit. An application must access a reader or writer's xfa property on a PDF whose corresponding stream uses /FlateDecode, after which decompression can exhaust process memory and interrupt service.

The record

CVE
CVE-2026-27888
Published
Feb 26, 2026
Updated
Feb 26, 2026
Vendor
py-pdf
Product
pypdf
Classifications
CWE-400, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 26, 2026Record 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=< 6.7.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

py-pdf · pypdfversion=< 6.7.3

Published CVSS scores

6.6GitHub, Inc.CVSS: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
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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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