Heap-based buffer overflow in XZ Utils - CVE-2026-34743
Published: July 22, 2026
Vulnerability identifier: #VU139114
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-34743
CWE-ID: CWE-122
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: tukaani.org
Affected software:
XZ Utils
XZ Utils
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a buffer overflow.
The vulnerability exists due to a heap-based buffer overflow in lzma_index_append() when appending records to an lzma_index previously produced by lzma_index_decoder() from an Index containing no Records. A remote attacker can trigger this code path to cause a buffer overflow.
The issue requires the uncommon sequence of decoding an Index with no Records and then appending Records to the resulting lzma_index.
How to mitigate CVE-2026-34743
Install security update from vendor's website.