Is CVE-2026-34743 in the CISA KEV catalog?

No. CVE-2026-34743 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-34743?

CVE-2026-34743 has a CVSS v3 base score of 5.3 (Low).

What is the EPSS score for CVE-2026-34743?

CVE-2026-34743 has an EPSS score of 0.35% (27th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-34743?

Upgrade xz-utils on debian unstable to 5.8.3-1 or later. Fixes are available for 4 affected products.

CVE & CISA-KEV Catalog

CVE-2026-34743

LOW

5.3

CVSS v3

NVD

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.

CWE-122Heap-based Buffer Overflow

How to fix

Remediation Available

xz-utilsDebian

Fixed in:5.8.3-1CVE-2026-34743

liblzma5Ubuntu

Fixed in:5.1.1alpha+20120614-2ubuntu2.14.04.1+esm2USN-8362-1

Fixed in:5.1.1alpha+20120614-2ubuntu2.16.04.1+esm2USN-8362-1

Fixed in:5.2.2-1.3ubuntu0.1+esm1USN-8362-1

Fixed in:5.2.4-1ubuntu1.1+esm1USN-8362-1

Fixed in:5.2.5-2ubuntu1.1USN-8362-1

Fixed in:5.6.1+really5.4.5-1ubuntu0.3USN-8362-1

Fixed in:5.8.1-1ubuntu0.1USN-8362-1

xz-utilsUbuntu

Fixed in:5.1.1alpha+20120614-2ubuntu2.14.04.1+esm2USN-8362-1

Fixed in:5.1.1alpha+20120614-2ubuntu2.16.04.1+esm2USN-8362-1

Fixed in:5.2.2-1.3ubuntu0.1+esm1USN-8362-1

Fixed in:5.2.4-1ubuntu1.1+esm1USN-8362-1

Fixed in:5.2.5-2ubuntu1.1USN-8362-1

Fixed in:5.6.1+really5.4.5-1ubuntu0.3USN-8362-1

Fixed in:5.8.1-1ubuntu0.1USN-8362-1

xzdecUbuntu

Fixed in:5.1.1alpha+20120614-2ubuntu2.14.04.1+esm2USN-8362-1

Fixed in:5.1.1alpha+20120614-2ubuntu2.16.04.1+esm2USN-8362-1

Fixed in:5.2.4-1ubuntu1.1+esm1USN-8362-1

Fixed in:5.2.5-2ubuntu1.1USN-8362-1

Fixed in:5.6.1+really5.4.5-1ubuntu0.3USN-8362-1

Fixed in:5.8.1-1ubuntu0.1USN-8362-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityLow

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Exploit Intelligence

0.35%probability of exploitation in 30 days

27thpercentile

Low risk: more likely to be exploited than 27% of all known CVEs.

References

Patch2

Vendor Advisory1

github.com

Release Notes1

github.com

Related Vulnerabilities

Other CWE-122 (Heap-based Buffer Overflow) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2015-3113	Critical	9.8	100%	KEV	Fix
CVE-2024-26256	High	7.8	88%	-	Fix
CVE-2020-25687	Medium	5.9	87%	-	Fix
CVE-2009-3459	High	8.8	86%	KEV	Fix
CVE-2021-21017	High	8.8	86%	KEV	-
CVE-2020-25683	Medium	5.9	86%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-15.