CVE-2026-120251
Received Received - Intake

Infinite Loop in imagecodecs via Malformed CCITT Group 4 Stream

Publication date: 2026-11-01

Last updated on: 2026-11-01

Assigner: VulnCheck

Description
imagecodecs 2026.3.6 through 2026.10.10 contains an infinite loop vulnerability in ccitt_fax4_decode_size() that allows attackers to hang the calling process by supplying a crafted CCITT Group 4 stream. Attackers can provide an 8-byte G4 stream lacking EOFB to ccittfax4_decode() or the numcodecs Ccittfax4 codec, consuming full CPU until the process is killed.

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Meta Information

Published
2026-11-01
Last Modified
2026-11-01
Generated
2026-11-01
AI Q&A
2026-11-01
EPSS Evaluated
N/A
NVD
CVE-2026-120251
EUVD
EUVD-2026-114748

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
cgohlke imagecodecs 2026.3.6

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-835 The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.

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Executive Summary

CVE-2026-120251 is an infinite loop vulnerability in the imagecodecs library affecting versions 2026.3.6 through 2026.10.10. It occurs in the ccitt_fax4_decode_size() function when processing a crafted 8-byte CCITT Group 4 stream lacking an EOFB marker. The loop condition fails to advance properly, causing the CPU to hang indefinitely until the process is killed.

Detection Guidance

To detect this vulnerability, monitor for processes consuming excessive CPU resources, particularly those running imagecodecs or related image processing tasks. Check for processes stuck in an infinite loop by examining CPU usage with system monitoring tools like top, htop, or ps. Look for processes named imagecodecs, ccittfax4_decode, or similar.

Impact Analysis

This vulnerability can cause denial-of-service by consuming full CPU resources until the process is terminated. It may lead to system slowdowns or crashes, disrupting applications relying on imagecodecs for processing CCITT Group 4 images.

Compliance Impact

This vulnerability primarily impacts system availability due to CPU exhaustion from an infinite loop, which could lead to service disruptions. For GDPR, this may affect availability of personal data processing systems, potentially violating Article 32 requirements for resilience. Under HIPAA, it could disrupt healthcare systems handling protected health information, impacting the Security Rule's integrity and availability requirements.

Mitigation Strategies

Immediately update the imagecodecs library to the latest version, as the vulnerability has been resolved in newer releases. If updating is not possible, restrict access to applications using imagecodecs or disable the CCITT Group 4 decoding functionality if not required. Monitor affected systems for unusual CPU usage or process hangs.

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