Vulnerability · Published Jul 1, 2026 · Assigned by runZero
CVE-2026-6687FatFs Stack Buffer Overflow via Uncapped exFAT Label Length
High 7.6
In plain English
A high-severity stack buffer overflow in FatFs from ChaN. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 29% of all known vulnerabilities).
Severity (CVSS 3.1)7.6High
Exploit odds (30 days)0.3%top 71.4% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known
Official description
FatFs R0.16 and earlier contains a stack overflow bug in f_getlabel() because exFAT label length (XDIR_NumLabel) is trusted without enforcing spec maximums. This maps to CWE-121 (Stack-based Buffer Overflow). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H (7.6, High). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total.
Affected products (as reported)
Weakness: CWE-121 · Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
References
- https://www.runzero.com/blog/fatfs-bugs/ third-party-advisory
- https://github.com/runZeroInc/vulns-2026-fatfs-chance technical-description
- https://elm-chan.org/fsw/ff/ product
- https://www.runzero.com/advisories/fatfs-exfat-label-len-of-cve-2026-6687/ third-party-advisory