CVE-2026-125742: 7-Zip memory corruption in LZX decoder

Summary

7-Zip versions before 26.06 contain a heap out-of-bounds write flaw in the LZX decoder used when extracting CAB archives. A local attacker who gets a victim to extract a crafted multi-volume CAB archive could corrupt memory and potentially run arbitrary code, and the victim must take action to open the file.

Read the original description

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.

cve.now Index

14Pcve.now Index 14 of 100 · methodology v3 · provisional

Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
Exposure5/25Specific setups only
Reach?/20Unknown. No tracked technology or package matched
Severity8.5/10CVSS 8.5
No patch0/5No signal

What would change the score

Would score about 64 if added to CISA KEV
Would score about 59 if CISA's SSVC rates exploitation active
Would score about 24 if CISA's SSVC rates it automatable

How the score works · Rankings

What to do

Check whether your setup matches what the bug needs.
7-Zip versions before 26.06 A continuation CAB volume declares a smaller window (multi-volume CAB archive extraction)
Upgrade to a fixed version: 26.06.

Check your systems with an agent

Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.

Check whether my systems are affected by CVE-2026-125742 (7-Zip before 26.06 Heap Out-of-Bounds Write via LZX Decoder in CAB Extraction), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-125742 (entry last updated 2026-11-10):
Affected:
- 7-Zip 7-Zip: fixed in 26.06
Fixed versions: 26.06.
Conditions (all must be true for the bug to be hit):
- 7-Zip versions before 26.06 (source: https://www.vulncheck.com/advisories/7-zip-before-26.06-heap-out-of-bounds-write-via-lzx-decoder-in-cab-extraction)
- A continuation CAB volume declares a smaller window (multi-volume CAB archive extraction) (source: https://www.vulncheck.com/advisories/7-zip-before-26.06-heap-out-of-bounds-write-via-lzx-decoder-in-cab-extraction)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: local access, no login, a user action.
CISA KEV: CVE-2026-125742 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-125742 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/ip7z/7zip/commit/d3296e39e1f1f92c7b41c0c3848e65640428d42d
- https://github.com/ip7z/7zip/releases/tag/26.06
- https://github.com/ip7z/7zip/blob/26.05/CPP/7zip/Compress/LzxDecoder.cpp#L1496-L1513
- https://www.vulncheck.com/advisories/7-zip-before-26.06-heap-out-of-bounds-write-via-lzx-decoder-in-cab-extraction
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Entry: https://cve.now/CVE-2026-125742
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-125742.

Timeline

Nov 10, 2026, 12:00 PM UTCCVE published
Nov 10, 2026, 12:03 PM UTCFirst seen by cve.now
Nov 10, 2026, 12:04 PM UTCRecord last updated

Affected versions

7-Zip 7-Zip
fixed in 26.06

Evidence 7

CVE record · 2

Establishes: The identifier and description.

Record
CVE List · CVE-2026-125742
Record
NVD · CVE-2026-125742

Public exploit code · 1

Establishes: Public exploit code exists (Exploit-DB, Metasploit, Nuclei and GitHub).

Exploit
potion-brew.pages.dev · posts/7zip-cab-lzx-window-desync-rce

Corrections

None so far.

Something wrong on this page? Report an error. Every fix is listed here.

Questions about CVE-2026-125742

Is CVE-2026-125742 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data

What does this mean?

A heap out-of-bounds write in the LZX decoder used during CAB extraction corrupts memory. The advisory says this can enable arbitrary code execution.Source: vulncheck.com

Which versions are affected by CVE-2026-125742?

7-Zip: before 26.06.Source: cve.now feed data

Am I affected, and how do I check?

7-Zip versions before 26.06 are affected, and only when extracting multi-volume CAB archives where a continuation volume declares a smaller window. To check, compare the installed 7-Zip version with 26.06 and see whether the archive is a multi-volume CAB.Source: vulncheck.com

How do I fix CVE-2026-125742?

Upgrade to 7-Zip 26.06 or later.Source: vulncheck.com

7-Zip before 26.06 Heap Out-of-Bounds Write via LZX Decoder in CAB Extraction