Bug 2561968 (CVE-2026-117556)

Summary: CVE-2026-117556 zchunk: zchunk: Denial of Service via malformed file header
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
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Priority: low    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in zchunk. This vulnerability allows a remote attacker to cause a Denial of Service (DoS) by tricking an application into processing a specially crafted file. Improper boundary checking during file header parsing causes the program to read beyond the allocated memory buffer, leading to an application crash.
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Description OSIDB Bzimport 2026-10-27 13:43:47 UTC 
zchunk before 1.5.5 contains a heap out-of-bounds read vulnerability in read_preface() in src/lib/header.c that passes the total header length instead of remaining bytes to compint parsing functions. Attackers can supply a crafted .zck file whose header ends inside a compressed integer, causing reads past the heap header buffer and crashing the application.