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CVE-2026-6686 affects FatFs R0.16 and earlier. When f_lseek() is used to extend a file beyond EOF, newly allocated clusters are not zero-filled before becoming readable through the extended file region. As a result, the file can expose residual data left in those clusters from prior filesystem use, including content from previously deleted files. The issue is an uninitialized resource exposure in file-extension handling rather than a memory-corruption flaw.
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No public exploit code observed for this vulnerability.
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
16 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A medium-severity information disclosure flaw in FatFs where uninitialized cluster exposure can leak stale data from previously deleted files when extending files past EOF.
An improper file extension handling flaw in FatFs that may expose residual data from previously deleted files.
A FatFs information disclosure flaw where seeking beyond EOF exposes uninitialized cluster data and can leak stale content from previously deleted files.
A FatFs information disclosure issue where extending a file past its end can expose residual data from previously deleted files.
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.