How severe is CVE-2026-34743?

CVE-2026-34743 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2026-34743 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34743?

CVE-2026-34743 affects Tukaani Xz. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34743?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-34743 have an EU (EUVD) identifier?

Yes. CVE-2026-34743 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18505.

When was CVE-2026-34743 published?

CVE-2026-34743 was published on 2026-04-02 and last updated on 2026-06-17.

CVE-2026-34743

CVE-2026-34743 is a medium-severity vulnerability in Tukaani Xz with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-122.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v4: 1.7
EPSS exploit prediction: 0% (27th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-18505
Weakness: CWE-122
Affected product: Tukaani Xz
Published: 2026-04-02
Last modified: 2026-06-17

Description

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

Frequently asked questions

What is CVE-2026-34743?: XZ Utils provide a general-purpose data-compression library plus command-line tools. Prior to version 5.8.3, if lzma_index_decoder() was used to decode an Index that contained no Records, the resulting lzma_index was left in a state where where a subsequent lzma_index_append() would allocate too little memory, and a buffer overflow would occur. This issue has been patched in version 5.8.3.
How severe is CVE-2026-34743?: CVE-2026-34743 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2026-34743 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34743?: CVE-2026-34743 affects Tukaani Xz. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34743?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-34743 have an EU (EUVD) identifier?: Yes. CVE-2026-34743 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18505.
When was CVE-2026-34743 published?: CVE-2026-34743 was published on 2026-04-02 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:tukaani:xz:*:*:*:*:*:*:*:*

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