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CVE-2026-50458 is an elevation-of-privilege vulnerability in Microsoft Brokering File System (BFS), implemented in the Windows kernel minifilter driver bfs.sys. The flaw is caused by a race condition in BFS internal directory handling that can lead to a use-after-free condition. Under concurrent operations on the same path, BFS can free kernel objects while they are still referenced, creating a kernel memory corruption primitive. An attacker with local authorized access can trigger the vulnerable condition, including from a low-privileged or sandboxed context, and leverage the resulting memory corruption to escalate privileges on affected Windows 11 and Windows Server 2025 systems.
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What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
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No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
8 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A high-severity local privilege escalation vulnerability in Microsoft’s Brokering File System (bfs.sys) caused by a race-condition-triggered use-after-free, allowing a local authenticated attacker or sandboxed code to corrupt kernel memory and escalate privileges to SYSTEM.
A use-after-free vulnerability in the Windows Brokering File System (bfs.sys) Windows kernel minifilter driver, patched in Microsoft's Patch Tuesday.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.