Microsoft Windows Backup Engine: Local privilege escalation via path equivalence
Summary
A flaw in the Windows Backup Engine (CWE-41, improper resolution of path equivalence) allows a locally authorized user to elevate privileges. CVSS v3.1 base score is 7.8 (High). Exploitation requires local access with low privileges and no user interaction; a successful attack gives the attacker high impact on confidentiality, integrity and availability.
Affected
- Windows 10 Version 21H2: builds 10.0.19044.0 to below 10.0.19044.7807
- Windows 10 Version 22H2: builds 10.0.19045.0 to below 10.0.19045.7807
- Windows 11 Version 23H2: builds 10.0.22631.0 to below 10.0.22631.7652
- Windows 11 Version 24H2: builds 10.0.26100.0 to below 10.0.26100.9711
- Windows 11 Version 25H2: builds 10.0.26200.0 to below 10.0.26200.9711
- Windows 11 Version 26H1: builds 10.0.28000.0 to below 10.0.28000.3231
- Windows 11 Version 26H2: builds 10.0.26300.0 to below 10.0.26300.9711
Fixed in
- Fixed in the October 2026 Patch Tuesday security update from Microsoft.
- Windows 10 Version 21H2: build 10.0.19044.7807 or later.
- Exact KB number for this CVE: Unknown.
Workaround
Unknown.
Exploitation
- CISA SSVC: exploitation none, not automatable, total technical impact.
- No confirmed active exploitation as of 2 November 2026.
Our recommendation
- Install the October 2026 Windows security update on all affected systems and verify the build number.
- Restrict local logon to trusted users and review accounts with local access.
- Monitor for unusual backup service activity and new privileged accounts or processes.
Information from Microsoft (Patch Tuesday October 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – Windows Backup Engine
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Windows, Windows ESU (Extended Security Updates)
- Updates (KB)
- KB5126657, KB5126653, KB5127648, KB5127646
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-70184 msrc.microsoft.com
- OpenCVE: CVE-2026-70184 app.opencve.io
- Vulners CVE List: CVE-2026-70184 vulners.com
- Vulners NVD: CVE-2026-70184 vulners.com
- Vulners VulnRichment: CVE-2026-70184 vulners.com
- SonicWall: Microsoft security bulletin coverage, October 2026 www.sonicwall.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 2 Nov 2026, 04:01.
Original description (NVD)
Improper resolution of path equivalence in Windows Backup Engine allows an authorized attacker to elevate privileges locally.
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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