Microsoft Windows BitLocker: Remote code execution via heap buffer overflow
Summary
A heap-based buffer overflow in Windows BitLocker allows an unauthenticated attacker to execute code over the network. The CNA record lists affected builds of Windows 11 (23H2, 24H2, 25H2, 26H1, 26H2) and Windows Server 2022 and 2025. Microsoft rates the CVSS base score as 9.8 (Critical) and lists the maximum severity as Important; the attack path and triggering service are not described in the sources.
Affected
- Windows 11 23H2 (x64 and ARM64): builds below 10.0.22631.7652
- Windows 11 24H2: builds below 10.0.26100.9711
- Windows 11 25H2: builds below 10.0.26200.9711
- Windows 11 26H1: builds below 10.0.28000.3231
- Windows 11 26H2: builds below 10.0.26300.9711
- Windows Server 2022: builds below 10.0.20348.5761
- Windows Server 2025 (including Server Core): builds below 10.0.26100.33650
- Build ranges are taken from third-party copies of the CNA data and should be verified on the MSRC page.
Fixed in
- Install the security update published by Microsoft for CVE-2026-96909 (released 2026-10-13).
- Fixed builds according to the CNA data: see the affected list above. Confirm the exact KB and build numbers on the MSRC Security Update Guide before rollout.
Workaround
Unknown. No vendor workaround or mitigation was identified; patching is the only documented remedy.
Exploitation
- No evidence of in-the-wild exploitation found.
- CISA SSVC (CNA/ADP data): exploitation none, automatable yes, technical impact total.
- Microsoft's score uses an unproven exploit maturity (E:U).
- CISA KEV listing could not be confirmed; check the KEV catalog.
- No public proof-of-concept found in the searches performed, which does not prove that none exists.
Our recommendation
- Inventory all Windows 11 and Windows Server systems and compare their builds with the affected list.
- Patch first on externally reachable systems and servers; verify the exact fixed build on the MSRC page.
- Check whether any hosts run an older build or an unsupported release that would not receive the fix.
- Determine which network services are exposed to untrusted networks, since the triggering path is not documented in the sources.
- Monitor for exploitation indicators and re-check the CISA KEV catalog and public PoC sources.
Information from Microsoft (Patch Tuesday October 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-96909 msrc.microsoft.com
- OpenCVE: CVE-2026-96909 app.opencve.io
- Vulners CVE list entry: CVE-2026-96909 vulners.com
- Strix: CVE-2026-96909 www.strix.ai
- VulDB: CVE-2026-96909 vuldb.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 30 Oct 2026, 18:16.
Original description (NVD)
Heap-based buffer overflow in Windows BitLocker allows an unauthorized attacker to execute code 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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