Windows: Path traversal in libarchive allows file tampering
Summary
Windows libarchive, the archive handling library built into several Windows 10, 11 and Server versions, contains a path traversal flaw (CWE-22). A remote attacker can tamper with files outside the intended directory. The attack needs no authentication, but a user must act, for example by opening or extracting a crafted archive (UI:R). The CVSS 3.1 base score is 6.5 (Medium), and no exploitation in the wild is known.
Affected
- Windows 10 Version 1809 and Windows Server 2019 (incl. Server Core): builds before 10.0.17763.9376
- Windows 10 Version 21H2: builds before 10.0.19044.7807
- Windows 10 Version 22H2: builds before 10.0.19045.7807 (one third-party mirror lists 19044.7807; verify against MSRC)
- Windows 11 versions 23H2, 24H2, 25H2, 26H1 and 26H2: builds before the versions listed in the MSRC advisory
- Windows Server 2022: builds before 10.0.20348.5761
- Windows Server 2025 (incl. Server Core): builds before 10.0.26100.33650
Fixed in
- Windows 10 1809 and Server 2019: KB5126651, build 10.0.17763.9376 (released 13 October 2026)
- Other affected versions: cumulative update of 13 October 2026 with the builds listed above; see the MSRC advisory for the update numbers
Workaround
Unknown. No vendor-documented workaround is known.
Exploitation
- No known exploitation in the wild and no public proof of concept for this CVE.
- Not listed in the CISA KEV catalogue at the time of research.
- EPSS 0.00708 (low exploitation probability).
Our recommendation
- Install the October 2026 Windows security update on all affected systems, starting with Windows 10 1809 and Server 2019 (KB5126651).
- Check for remaining Windows 10 21H2 or 22H2 clients and make sure they receive the matching builds.
- Until patched, block or quarantine archives from untrusted sources at the mail gateway and file shares, and restrict who can open them.
- Apply the update as a whole, because it also fixes CVE-2026-69639 (CVSS 9.8).
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Tampering – Windows Libarchive
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Windows, Windows ESU (Extended Security Updates)
- Updates (KB)
- KB5126651, KB5126655, KB5126657, KB5126646, KB5127648, KB5126653
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-69973 msrc.microsoft.com
- Microsoft KB5126651 Windows 10 1809 security update support.microsoft.com
- Vulners MSCVE record MS:CVE-2026-69973 vulners.com
- Strix CVE record CVE-2026-69973 www.strix.ai
- OpenCVE CVE-2026-69973 app.opencve.io
- Tenable plugin for KB5126651 www.tenable.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 5 Nov 2026, 11:25.
Original description (NVD)
Improper limitation of a pathname to a restricted directory ('path traversal') in Windows Libarchive allows an unauthorized attacker to perform tampering over a network.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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