CVE-2026-40260Network attack vector

Memory exhaustion via quadratic XMP entity expansion

Published Apr 16, 2026 · Updated Apr 16, 2026

XML entity expansion in XMP parsing in py-pdf pypdf before 6.10.0 allows remote attackers to exhaust memory with a crafted PDF. XmpInformation passes untrusted XMP bytes to xml.dom.minidom.parseString, whose Expat limits do not block quadratic custom-entity expansion. The condition is reached only when an application parses the document's XMP metadata, allowing repeated entity references to inflate a small declaration until process or host RAM is exhausted and service is interrupted.

CVSS severity6.9
Medium
EPSS probability0.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

XML entity expansion in XMP parsing in py-pdf pypdf before 6.10.0 allows remote attackers to exhaust memory with a crafted PDF. XmpInformation passes untrusted XMP bytes to xml.dom.minidom.parseString, whose Expat limits do not block quadratic custom-entity expansion. The condition is reached only when an application parses the document's XMP metadata, allowing repeated entity references to inflate a small declaration until process or host RAM is exhausted and service is interrupted.

The record

CVE
CVE-2026-40260
Published
Apr 16, 2026
Updated
Apr 16, 2026
Vendor
py-pdf
Product
pypdf
Classifications
CWE-776, CAPEC-197, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 16, 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=< 6.10.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

py-pdf · pypdfversion=< 6.10.0

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
6.9GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-776Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
CAPEC-197Exponential Data Expansion
T1499.004Endpoint Denial of Service: Application or System Exploitation

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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