CVE-2026-120251: imagecodecs 2026.3.6 through 2026.10.10 Infinite Loop via ccittfax4_decode()

Published Nov 1, 2026

Updated

imagecodecs 2026.3.6 through 2026.10.10 contains an infinite loop vulnerability in ccittfax4decodesize() 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 ccittfax4decode() or the numcodecs Ccittfax4 codec, consuming full CPU until the process is killed.

Event History

Nov 1, 2026

CVE Published

via MITRE·12:57 AM

Data Sourced

via MITRE·12:57 AM

DescriptionSeverityWeakness

Data Sourced

via NVD·01:17 AM

DescriptionSeverityWeakness

Frequently Asked Questions

Which deployments are exposed to this issue?

Applications using imagecodecs to decode attacker-controlled CCITT Group 4 data through ccittfax4_decode() or the numcodecs Ccittfax4 codec are exposed. The impact is a denial of service against the calling process through sustained CPU consumption.

What must an attacker do to trigger the problem?

The attacker must cause the application to process a crafted 8-byte CCITT Group 4 stream that lacks an EOFB marker. The CVSS vector indicates user interaction is required.

How can I identify affected installations?

Installations running imagecodecs versions 2026.3.6 through 2026.10.10 are affected according to the reported version range. Review whether those installations invoke the affected decoder or codec on untrusted image data.

CVE-2026-120251: imagecodecs 2026.3.6 through 2026.10.10 Infinite Loop via ccittfax4_decode()

Event History

Frequently Asked Questions

Which deployments are exposed to this issue?

What must an attacker do to trigger the problem?

How can I identify affected installations?

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Frequently Asked Questions

Which deployments are exposed to this issue?

What must an attacker do to trigger the problem?

How can I identify affected installations?