Bug 2565166

Summary: CVE-2026-120251 python-imagecodecs: imagecodecs: Denial of Service via infinite loop in CCITT Group 4 decoding [fedora-43]
Product: [Fedora] Fedora Reporter: Oleg Sushchenko <osushche>
Component: python-imagecodecsAssignee: Orion Poplawski <orion>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: 43CC: orion
Target Milestone: ---Keywords: Security, SecurityTracking
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Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["d383bd98-28d0-4044-a3e1-9dcc6a97eaa2"]}
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On:    
Bug Blocks: 2564500    

Description Oleg Sushchenko 2026-11-02 13:11:39 UTC 
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

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.