CVE-2021-37819Public exploitNetwork attack vector

Denial of service via cyclic PDF page tree

Published Sep 9, 2022 · Updated Aug 4, 2024

Infinite-loop denial of service in PDF Labs pdftk-java 3.2.3 allows attackers to hang PDF processing with a crafted PDF. PdfReader.PageRefs.iteratePages recursively follows a page-tree Kids reference without detecting when a child points back to its parent, so traversal never terminates. Processing the malformed file is the required gate, and the resulting loop consumes the affected process without reported data disclosure or modification.

CVSS severity7.5
High
EPSS probability0.81%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Infinite-loop denial of service in PDF Labs pdftk-java 3.2.3 allows attackers to hang PDF processing with a crafted PDF. PdfReader.PageRefs.iteratePages recursively follows a page-tree Kids reference without detecting when a child points back to its parent, so traversal never terminates. Processing the malformed file is the required gate, and the resulting loop consumes the affected process without reported data disclosure or modification.

The record

CVE
CVE-2021-37819
Published
Sep 9, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-835, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 9, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

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.

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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')
T1499.004Endpoint Denial of Service: Application 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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