Is CVE-2026-6687 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-6687 being exploited in the wild.

How severe is CVE-2026-6687?

High severity, with a CVSS score of 7.6, published 1 July 2026.

Is there a fix for CVE-2026-6687?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-6687 attacked?

It is attacked with physical access, in a software library.

Am I affected by CVE-2026-6687?

Check whether you run ChaN FatFs at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-6687: ChaN FatFs stack overflow in f_getlabel

CVE-2026-6687 · Severity: high · CVSS 7.6 · Published 2026-07-01

FatFs is a widely used software library that allows embedded devices, such as industrial controllers and consumer electronics, to read and write data to SD cards and USB drives. A security flaw in how the library handles disk labels allows a specially crafted storage device to crash the system or potentially take control of the device when it is plugged in. This could lead to a complete compromise of the affected hardware, impacting operations or allowing unauthorized access to sensitive data stored on the device.

Technologies: ChaN FatFs. Vendors: ChaN.

Quick answers

Is CVE-2026-6687 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-6687 being exploited in the wild.
How severe is CVE-2026-6687?: High severity, with a CVSS score of 7.6, published 1 July 2026.
Which products and versions are affected?: ChaN FatFs R0.16 and earlier.
Is there a fix for CVE-2026-6687?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-6687 attacked?: It is attacked with physical access, in a software library.
Am I affected by CVE-2026-6687?: Check whether you run ChaN FatFs at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A stack-based buffer overflow (CWE-121) exists in the f_getlabel() function of FatFs R0.16 and earlier. The vulnerability is caused by the software trusting the exFAT volume label length field (XDIR_NumLabel) from the disk without validating it against the specification maximum of 11 characters. Because XDIR_NumLabel is a byte, an attacker can specify a much larger value (up to 255), causing a loop to copy data into fixed-size stack buffers (typically 12 or 24 bytes) used by calling applications. This physical attack vector requires the insertion of a maliciously formatted exFAT storage device. Successful exploitation can lead to arbitrary code execution on bare-metal targets that lack modern memory protections.

Affected products

ChaN (elm-chan.org) FatFs R0.16 and earlier

Timeline

2026-03-17: disclosed: Initial findings discovered by runZero researchers
2026-04-20: other: CVE IDs reserved and initial outreach to vendor
2026-07-01: advisory: Public advisory published by runZero and NVD

References

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