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CVE-2026-72971 is a local tampering vulnerability in the Windows Container Isolation FS Filter Driver, unionfs.sys. The flaw is caused by improper link resolution before file access, also known as link following, which can cause the driver to operate on an unintended target. Microsoft classifies the issue as CWE-59 and rates it Important with a CVSS v3.1 base score of 5.5. Successful exploitation allows an authorized local attacker to abuse the vulnerable file-access logic to tamper with data or files that should not be modified through the intended access path. Available reporting indicates the issue is particularly relevant to Windows container or containerized workload scenarios and affects Windows 11 version 26H1 before the fixed build identified by Microsoft.
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What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
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.
27 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A zero-day tampering vulnerability in the Windows Container Isolation FS Filter Driver (unionfs.sys) that Microsoft says attackers could exploit and that was publicly disclosed before a patch was available.
A publicly disclosed elevation-of-privilege vulnerability in the Windows Container Isolation FS Filter Driver (unionfs.sys) that lets an authenticated local attacker access another local user's registry hive and potentially escalate to administrator privileges.
Privilege escalation vulnerability in the Windows Container Isolation FS Filter Driver (unionfs.sys).
A publicly disclosed local tampering vulnerability described as low impact and unlikely to be exploited.
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.