CVE-2021-39562Public exploit

Converter crash via recursive PDF stream resolution

Published Sep 20, 2021 · Updated Aug 4, 2024

Denial of service in SWFTools through 20200710 allows context-dependent attackers to crash pdf2swf with a crafted PDF file. While resolving PDF stream objects, the xpdf parser repeatedly cycles through FileStream::makeSubStream, XRef::fetch, and Parser::makeStream until stack exhaustion aborts the process. Exploitation requires a user or workflow to process the file locally; the demonstrated effect is termination of the converter, not data disclosure or modification.

CVSS severity5.5
Medium
EPSS probability0.64%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Denial of service in SWFTools through 20200710 allows context-dependent attackers to crash pdf2swf with a crafted PDF file. While resolving PDF stream objects, the xpdf parser repeatedly cycles through FileStream::makeSubStream, XRef::fetch, and Parser::makeStream until stack exhaustion aborts the process. Exploitation requires a user or workflow to process the file locally; the demonstrated effect is termination of the converter, not data disclosure or modification.

The record

CVE
CVE-2021-39562
Published
Sep 20, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 20, 2021CVE 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P
5.5NIST NVDCVSS: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.

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo