7-Zip: LZX decoder heap out-of-bounds write (CVE-2026-125742)
7-Zip versions prior to 26.06 contain a heap out-of-bounds write vulnerability in the LZX decoder that can lead to arbitrary code execution when processing crafted multi-volume CAB archives.
CVE search metadata
CVE search record: CVE-2026-125742. Severity: high. CVSS: 7.8. KEV: no. Product: 7-Zip (< 26.06). Brief: 7-Zip: LZX decoder heap out-of-bounds write (CVE-2026-125742). Brief link: https://feed.craftedsignal.io/briefs/2026-11-09-7zip-heap-overflow/
Triage facts
Revision 1- Applicability
- 7-Zip (< 26.06)
- Evidence
- Unknown
- Severity
- High
- Action
- Elevated
- Sources
- 1 public source
- Freshness
- Revision 1Nov 10, 14:33 UTC
- Vulnerabilities
- 1 CVE
- Source quality
- A2Roughly even chance
7-Zip versions before 26.06 are vulnerable to a heap out-of-bounds write vulnerability within the LZX decoder. The issue arises when the software processes multi-volume CAB archives where a continuation volume declares a smaller window size than the original. This discrepancy results in a stale _pos value that bypasses internal bounds checks, potentially allowing for arbitrary code execution if a user extracts a malicious CAB archive.
Impact
Successful exploitation allows for arbitrary code execution in the context of the user running the 7-Zip extraction process.
Recommendation
- Update 7-Zip to version 26.06 or later across all managed endpoints to remediate CVE-2026-125742.
- Restrict the opening of untrusted multi-volume CAB files until software updates are applied.
Threat Hunt
Identify endpoints executing 7-Zip command line utilities or GUI processes on untrusted multi-volume CAB files
Data: Process creation logs (Event ID 1) containing 7z.exe or 7zg.exe, File access/CLI argument logs showing .cab extensions
Mitigations
Upgrade 7-Zip to version 26.06 or later
CVE-2026-125742