CVE detail
CVE-2026-6686
FatFs R0.16 and earlier contains an uninitialized cluster exposure when f_lseek() extends files beyond EOF without zero-filling newly allocated clusters. This maps to CWE-908 (Use of Uninitialized Resource). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N (4.6, Medium). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Partial.
Buzz score
Why this CVE is surfacing
This all-time snapshot uses the same composite formula as Trending across a 30-year evidence window, rather than a current rolling window.
Buzz score components · mention 19.5 · diversity 18.0 · KEV 0.0 · OTX 0.0 · PoC 4.5
Why it matters now
Mention timeline
- Total mentions
- 6
- within the 30d window
- Peak daily
- 4
- highest bucket
Evidence
Source links by recency
6 source links · newest first
- Seven Bugs in FatFs Put IoT and Embedded Devices at RiskSecurity Affairs
runZero found 7 flaws in FatFs, a filesystem used in IoT and embedded devices. Bugs can cause memory corruption, crashes, or data leaks via crafted storage. Cybersecurity firm runZero has disclosed seven vulnerabilities in FatFs, a compact open-source library that lets embedded devices read and write FAT and exFAT formatted storage, the same formats used […]
newssecurityaffairs.comJul 6, 2026, 10:20 AM d, and FatFs mishandles the bad data. runZero rated the set CVSS Medium to High, with no Criticals. The headline bug is CVE-2026-6682 (CVSS 7.6), an integer overflow in the code that mounts a FAT32 volume. Bad math can produce a false file size, which later code treats as a real read length. On real hardware, that can become memory corruption and code
newsthehackernews.comJul 3, 2026, 8:19 PM- https://www.runzero.com/blog/fatfs-bugs/www.runzero.com
No excerpt available.
Exploitwww.runzero.comJul 1, 2026, 3:17 PM No excerpt available.
Exploitwww.runzero.comJul 1, 2026, 3:17 PMNo excerpt available.
Exploitgithub.comJul 1, 2026, 3:17 PM- https://elm-chan.org/fsw/ff/elm-chan.org
No excerpt available.
Productelm-chan.orgJul 1, 2026, 3:17 PM
Exploit code
Public exploit repository references
Public PoC repositories are third-party, potentially unsafe artifacts. Treat their code as untrusted and use it only on authorized systems in an isolated, least-privilege environment. cvebuzz does not execute the code or verify that an exploit works.
1 repository references · best confidence 0.90 · max 0 stars
- runZeroInc/vulns-2026-fatfs-chanceHigh confidencegithubNVD Exploit reference0 starsDiscovered Jul 20, 2026, 12:20 AM
NVD labels the source link as Exploit; this is not independent verification of the repository's code.
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