CVE-2026-27628Public exploitNetwork attack vector

Application hang via circular cross-reference offsets

Published Feb 25, 2026 · Updated Feb 25, 2026

Infinite loop in pypdf before 6.7.2 allows attackers to hang applications by supplying a PDF with circular /Prev references. The _read_xref_tables_and_trailers() loop follows each cross-reference /Prev offset without tracking visited offsets, so a cycle re-parses the same objects indefinitely. An application must read the crafted file; the affected process consumes a CPU core and does not complete, interrupting that application's PDF-processing 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

Infinite loop in pypdf before 6.7.2 allows attackers to hang applications by supplying a PDF with circular /Prev references. The _read_xref_tables_and_trailers() loop follows each cross-reference /Prev offset without tracking visited offsets, so a cycle re-parses the same objects indefinitely. An application must read the crafted file; the affected process consumes a CPU core and does not complete, interrupting that application's PDF-processing service.

The record

CVE
CVE-2026-27628
Published
Feb 25, 2026
Updated
Feb 25, 2026
Vendor
py-pdf
Product
pypdf
Classifications
CWE-835, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 25, 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=< 6.7.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

py-pdf · pypdfversion=< 6.7.2

Published CVSS scores

1.2GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:L/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 exploitPublished

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499Endpoint Denial of Service

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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