CVE-2026-34743: XZ Utils: Buffer overflow in lzma_index_append()

Published Apr 2, 2026
·
Updated

Last updated 2 June 2026

Other sources

XZ Utils provide a general-purpose data-compression library plus command-line tools. Prior to version 5.8.3, if lzmaindexdecoder() was used to decode an Index that contained no Records, the resulting lzmaindex was left in a state where where a subsequent lzmaindexappend() would allocate too little memory, and a buffer overflow would occur. This issue has been patched in version 5.8.3.

— MITRE

XZ Utils: Buffer overflow in lzmaindexappend()

— Microsoft

Affected Software

11 affected componentsFixes available
Microsoft azl3 xz 5.4.4-2
Patch available
Microsoft cbl2 xz 5.2.5-1
Patch available
debian/xz-utils<=5.2.5-2.1~deb11u1, <=5.4.1-1, <=5.8.1-1
5.8.3-1
Tukaani XZ<5.8.3
IBM API Connect<=V10.0.8.0 - V10.0.8.9
Microsoft azl3 xz 5.4.4-2<5.4.4-3
5.4.4-3
Microsoft cbl2 xz 5.2.5-1<5.2.5-2
5.2.5-2
Microsoft azl3 rust 1.90.0-6<1.90.0-7
1.90.0-7
Microsoft azl3 xz 5.4.4-3<5.4.4-3
5.4.4-3
Microsoft azl3 rust 1.75.0-27<1.75.0-28
1.75.0-28
Microsoft cbl2 rust 1.72.0-15<1.72.0-16
1.72.0-16

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade debian/xz-utils to a version that resolves this vulnerability.

    Fixed in 5.8.3-1
  2. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 5.4.4-3
  3. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 5.2.5-2
  4. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 1.90.0-7
  5. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 1.75.0-28
  6. Upgrade

    Upgrade to a fixed release to a version that resolves this vulnerability.

    Fixed in 1.72.0-16
  7. Upgrade

    Upgrade XZ Utils to a version that resolves this vulnerability.

    Fixed in 5.8.3

Event History

Apr 2, 2026
CVE Published
via MITRE·06:36 PM
Data Sourced
via MITRE·06:36 PM
DescriptionWeakness
Data Sourced
via NVD·07:21 PM
RemedyDescriptionSeverityWeaknessAffected Software
Apr 4, 2026
Data Sourced
via Microsoft·08:02 AM
DescriptionSeverityWeaknessAffected Software
Updated
via Microsoft·08:02 AM
Affected Software
Updated
via Microsoft·08:02 AM
DescriptionSeverity
Updated
via Microsoft·08:02 AM
DescriptionSeverityWeakness
Jun 2, 2026
Data Sourced
via Ubuntu·12:37 PM
RemedyDescriptionSeverityAffected Software
Data Sourced
via Debian·12:38 PM
DescriptionAffected Software
Data Sourced
via Launchpad·12:38 PM
Description
Jul 7, 2026
Data Sourced
via IBM·12:00 AM
DescriptionAffected Software

Parent advisories

This vulnerability appears in the following advisories.

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