CVE-2021-31812

Application hang via overlong object-stream offset parsing

Published Jun 12, 2021 · Updated Aug 3, 2024

Denial of service in Apache PDFBox 2.0.23 and earlier allows local users to hang PDF-processing applications via a crafted PDF. PDFObjectStreamParser.readOffsets trusts the object-stream /N count and reads object numbers beyond their reserved stream region instead of stopping at the first-object boundary. A victim application must load attacker-controlled PDF content; the parser then fails to return, tying up its processing thread without reported confidentiality or integrity impact.

CVSS severity5.5
Medium
EPSS probability3.05%
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 Apache PDFBox 2.0.23 and earlier allows local users to hang PDF-processing applications via a crafted PDF. PDFObjectStreamParser.readOffsets trusts the object-stream /N count and reads object numbers beyond their reserved stream region instead of stopping at the first-object boundary. A victim application must load attacker-controlled PDF content; the parser then fails to return, tying up its processing thread without reported confidentiality or integrity impact.

The record

CVE
CVE-2021-31812
Published
Jun 12, 2021
Updated
Aug 3, 2024
Vendor
The Apache Software Foundation
Product
Apache PDFBox
Classifications
CWE-835, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 12, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Apache PDFBox <2.0.24

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache PDFBoxversion=Apache PDFBox <2.0.24

Published CVSS scores

5.5GitLab Advisory DatabaseCVSS:3.1/AV:L/AC:L/PR:N/UI:R/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)
Vectorlocal
Privilegesunauthenticated
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.

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Technologies

Your stack

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Your stack

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