Heap-based buffer overflow in XZ Utils - CVE-2026-34743

Vulnerability identifier: #VU139114

CSH Severity: Medium

CVSS v4: 8.2 [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]

CVE-ID: CVE-2026-34743

CWE-ID: CWE-122

Exploitation vector: Remote access

Exploit availability: No public exploit available

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.

XZ Utils
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Micro
SUSE Linux Enterprise Micro for Rancher
SUSE Linux Micro
Ubuntu
Basesystem Module
openSUSE Leap
openEuler
Anolis OS
liblzma5-debuginfo-32bit
liblzma5-32bit
xz-lang
liblzma5
xz-debugsource
xz-debuginfo
liblzma5-debuginfo
xz
xz-devel
xz-utils (Ubuntu package)
liblzma5-32bit-debuginfo
xz-static-devel
xz-help
xz-lzma-compat
xz-libs
xz-devel-64bit
liblzma5-64bit
xz-devel-32bit
liblzma5-64bit-debuginfo
xz-static

Install security update from vendor's website.

XZ Utils - update to 5.8.3
liblzma5-debuginfo-32bit - update to 5.0.5-6.10.1
liblzma5-32bit - addressed in versions 5.0.5-6.10.1, 5.2.3-150000.4.10.1, 5.4.1-150600.3.6.1
xz-lang - addressed in versions 5.0.5-6.10.1, 5.2.3-150000.4.10.1, 5.4.1-150600.3.6.1
liblzma5 - addressed in versions 5.0.5-6.10.1, 5.2.3-150000.4.10.1, 5.4.1-150600.3.6.1, 5.4.3-slfo.1.1_3.1, 5.4.3-6.1
xz-debugsource - addressed in versions 5.0.5-6.10.1, 5.2.3-150000.4.10.1, 5.4.1-150600.3.6.1, 5.4.3-slfo.1.1_3.1, 5.4.3-6.1
xz-debuginfo - addressed in versions 5.0.5-6.10.1, 5.2.3-150000.4.10.1, 5.4.1-150600.3.6.1, 5.4.3-slfo.1.1_3.1, 5.4.3-6.1
liblzma5-debuginfo - addressed in versions 5.0.5-6.10.1, 5.2.3-150000.4.10.1, 5.4.1-150600.3.6.1, 5.4.3-slfo.1.1_3.1, 5.4.3-6.1
xz - addressed in versions 5.0.5-6.10.1, 5.2.3-150000.4.10.1, 5.4.1-150600.3.6.1, 5.4.3-slfo.1.1_3.1, 5.4.3-6.1
xz-devel - addressed in versions 5.0.5-6.10.1, 5.2.3-150000.4.10.1, 5.4.1-150600.3.6.1
xz-utils (Ubuntu package) - addressed in versions 5.1.1 alpha+20120614-2ubuntu2.14.04.1+esm2, 5.1.1 alpha+20120614-2ubuntu2.16.04.1+esm2, 5.2.2-1.3ubuntu0.1+esm1, 5.2.4-1ubuntu1.1+esm1, 5.2.5-2ubuntu1.1, 5.6.1+really5.4.5-1ubuntu0.3, 5.8.1-1ubuntu0.1
liblzma5-32bit-debuginfo - addressed in versions 5.2.3-150000.4.10.1, 5.4.1-150600.3.6.1
xz-static-devel - addressed in versions 5.2.3-150000.4.10.1, 5.4.1-150600.3.6.1
xz-devel - update to 5.2.5-5
xz-help - update to 5.2.5-5
xz-lzma-compat - update to 5.2.5-5
xz-libs - update to 5.2.5-5
xz-debugsource - update to 5.2.5-5
xz-debuginfo - update to 5.2.5-5
xz - update to 5.2.5-5
xz-devel-64bit - update to 5.4.1-150600.3.6.1
liblzma5-64bit - update to 5.4.1-150600.3.6.1
xz-devel-32bit - update to 5.4.1-150600.3.6.1
liblzma5-64bit-debuginfo - update to 5.4.1-150600.3.6.1
xz-libs - update to 5.4.7-4
xz-lzma-compat - update to 5.4.7-4
xz-static - update to 5.4.7-4
xz-devel - update to 5.4.7-4
xz - update to 5.4.7-4

• https://github.com/tukaani-project/xz/security/advisories/GHSA-x872-m794-cxhv

• Heap-based buffer overflow in XZ Utils
• openEuler update for xz
• SUSE update for xz
• SUSE update for xz
• SUSE update for xz
• SUSE update for xz
• SUSE update for xz
• Anolis OS update for xz
• Ubuntu update for xz-utils