CVE-2026-117556 zchunk before 1.5.5 Heap Out-of-Bounds Read via read_preface()

Medium 5.3 Published 27 Oct 2026 Updated 28 Oct 2026

Exploited in the wild: Not known
Fix: None listed

What is CVE-2026-117556?

CVE-2026-117556 is a medium-severity vulnerability in zchunk, published on 27 Oct 2026.

Official description

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.

Weakness: CWE-125

Which versions are affected by CVE-2026-117556?

How do I fix CVE-2026-117556?

No fix has been published for CVE-2026-117556 yet. Limit exposure of the affected software until one is available.

Is CVE-2026-117556 being exploited?

There is no known exploitation of CVE-2026-117556 in the wild and no public exploit code.

Sources

Also known as AZL-111188, DEBIAN-CVE-2026-117556, GHSA-xcf7-q4j8-4wvv, UBUNTU-CVE-2026-117556.