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CVE-2026-6685 affects FatFs R0.16 and earlier. The vulnerability is an unsigned-subtraction wraparound in dirty-cache handling in the f_read() and f_write() paths, specifically involving the expression fp->sect - sect < cc during interleaved read/write activity on fragmented filesystems. On fragmented volumes, the arithmetic underflow can cause the implementation to incorrectly treat stale dirty cache state as valid or skip necessary cache handling, leading to stale-cache behavior and out-of-bounds memory effects in the read/write paths. The issue is described as an integer underflow/wraparound condition and maps to CWE-191.
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9 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A medium-severity unsigned subtraction wrap flaw in FatFs dirty-cache handling on fragmented volumes that can cause memory corruption or silent data corruption.
An integer wraparound flaw in FatFs cache handling for fragmented volumes that may silently corrupt stored data.
A FatFs vulnerability caused by unsigned-subtraction wraparound in dirty-cache handling on fragmented volumes, leading to stale cache behavior, out-of-bounds memory effects, and possible silent data corruption.
A FatFs cache-handling integer wrap on fragmented volumes that can silently corrupt data.
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Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.