CVE-2026-117556 PUBLISHED

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.

• HaiND from the Post and Telecommunication Institute of Technology finder

• GitHub Issue #119
• https://github.com/zchunk/zchunk
• https://github.com/zchunk/zchunk/commit/02b371a64bf98245df97315d07c684a0ca5ea1df
• zchunk 1.5.5 Release Notes
• https://github.com/zchunk/zchunk/blob/1.5.4/src/lib/header.c#L167
• VulnCheck Advisory: zchunk before 1.5.5 Heap Out-of-Bounds Read via read_preface()

• Out-of-bounds Read CWE