# CVE-2026-125742: 7-Zip before 26.06 Heap Out-of-Bounds Write via LZX Decoder in CAB Extraction

Status: published. Published: 2026-11-10. Updated: 2026-11-12.

7-Zip before 26.06 contains a heap out-of-bounds write vulnerability in the LZX decoder that lets attackers corrupt memory when a continuation CAB volume declares a smaller window. Attackers can entice victims to extract crafted multi-volume CAB archives, where a stale _pos value bypasses bounds checks, enabling arbitrary code execution.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/ip7z/7zip/commit/d3296e39e1f1f92c7b41c0c3848e65640428d42d

## Affected products and versions

- 7-Zip / 7-Zip: ≥ 0; < 26.06 (affected, custom). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 8.5 (high); CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 7.8 (high); CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H; source: CNA: VulnCheck

- CVSS 4.0: 8.5 (high); CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 7.8 (high); CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.18% as of 2026-11-12; percentile 7.57%

- SSVC: exploitation poc; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-787

## Exploit evidence

- exploit: https://potion-brew.pages.dev/posts/7zip-cab-lzx-window-desync-rce/ (CNA: VulnCheck)

## References

- https://github.com/ip7z/7zip/commit/d3296e39e1f1f92c7b41c0c3848e65640428d42d (CNA: VulnCheck; patch)

- https://github.com/ip7z/7zip/releases/tag/26.06 (CNA: VulnCheck; release-notes)

- https://github.com/ip7z/7zip/blob/26.05/CPP/7zip/Compress/LzxDecoder.cpp#L1496-L1513 (CNA: VulnCheck; product)

- https://potion-brew.pages.dev/posts/7zip-cab-lzx-window-desync-rce/ (CNA: VulnCheck; technical-description, exploit)

- https://www.vulncheck.com/advisories/7-zip-before-26.06-heap-out-of-bounds-write-via-lzx-decoder-in-cab-extraction (CNA: VulnCheck; third-party-advisory)

- https://github.com/ip7z/7zip/blob/26.05/CPP/7zip/Compress/LzxDecoder.cpp#L1496-L1513 (disclosure@vulncheck.com)

- https://github.com/ip7z/7zip/commit/d3296e39e1f1f92c7b41c0c3848e65640428d42d (disclosure@vulncheck.com)

- https://github.com/ip7z/7zip/releases/tag/26.06 (disclosure@vulncheck.com)

- https://potion-brew.pages.dev/posts/7zip-cab-lzx-window-desync-rce/ (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/7-zip-before-26.06-heap-out-of-bounds-write-via-lzx-decoder-in-cab-extraction (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-125742; retrieved 2026-11-12; source updated 2026-11-12

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-125742; retrieved 2026-11-10; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-125742; retrieved 2026-11-12; source updated Not reported

Revision: 913d5af60fa942132c48b2f857532d2cb1df499d65b66b0bfadfb374e28b3c21

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