CVE-2026-27024

Denial of service via cyclic TreeObject traversal

Published Feb 20, 2026 · Updated Feb 20, 2026

Denial of service in py-pdf pypdf before 6.7.1 allows attackers to hang PDF-processing code by supplying a crafted PDF. TreeObject.children follows the /First and /Next outline chain toward /Last without tracking visited child objects, so a cyclic reference prevents the iterator from terminating. Processing reaches the flaw only when an application accesses the crafted tree's children, such as while reading outlines, and the affected process remains stuck in the loop.

CVSS severity6.9
Medium
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in py-pdf pypdf before 6.7.1 allows attackers to hang PDF-processing code by supplying a crafted PDF. TreeObject.children follows the /First and /Next outline chain toward /Last without tracking visited child objects, so a cyclic reference prevents the iterator from terminating. Processing reaches the flaw only when an application accesses the crafted tree's children, such as while reading outlines, and the affected process remains stuck in the loop.

The record

CVE
CVE-2026-27024
Published
Feb 20, 2026
Updated
Feb 20, 2026
Vendor
py-pdf
Product
pypdf
Classifications
CWE-835, T1499.004
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Feb 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 20, 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=< 6.7.1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

py-pdf · pypdfversion=< 6.7.1

Published CVSS scores

6.9GitHub, Inc.CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/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)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499.004Application 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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