Is CVE-2026-6684 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-6684 being exploited in the wild.

How severe is CVE-2026-6684?

Medium severity, with a CVSS score of 4.6, published 1 July 2026.

Which products and versions are affected?

ChaN FatFs Prior to R0.16 with FF_LBA64 = 1 enabled.

Is there a fix for CVE-2026-6684?

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-2026-6684 attacked?

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

Am I affected by CVE-2026-6684?

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-2026-6684: ChaN FatFs infinite loop in GPT partition scanning

CVE-2026-6684 · Severity: medium · CVSS 4.6 · Published 2026-07-01

FatFs is a widely used software library that allows small embedded devices, such as industrial controllers and consumer electronics, to read files from storage media like SD cards. A flaw in how the library handles certain partition data allows a specially crafted storage device to cause the system to hang indefinitely during startup. This can result in a permanent denial of service, preventing the device from booting or functioning until the malicious storage media is removed or the firmware is recovered.

Technologies: ChaN FatFs. Vendors: ChaN.

Quick answers

Is CVE-2026-6684 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-6684 being exploited in the wild.
How severe is CVE-2026-6684?: Medium severity, with a CVSS score of 4.6, published 1 July 2026.
Which products and versions are affected?: ChaN FatFs Prior to R0.16 with FF_LBA64 = 1 enabled.
Is there a fix for CVE-2026-6684?: 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-2026-6684 attacked?: It is attacked with physical access, in a software library.
Am I affected by CVE-2026-6684?: 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 vulnerability classified as CWE-835 (Loop with Unreachable Exit Condition) exists in FatFs prior to version R0.16 when configured with 'FF_LBA64 = 1'. The issue stems from the GPT partition scanning logic, which trusts the partition-entry count (GPTH_PtNum) provided by the on-disk GPT header without sufficient validation or hard caps. An attacker with physical access can provide a crafted GPT image with a maximized partition count (e.g., 0xFFFFFFFF), forcing the library into a massive read loop during the mount process. This typically results in a system hang or boot failure, especially on bare-metal targets lacking a watchdog timer. The issue was addressed in R0.16 by adding the test_gpt_header() function to validate partition counts and CRCs.

Affected products

ChaN FatFs Prior to R0.16 with FF_LBA64 = 1 enabled

Timeline

2026-03-17: disclosed: Initial findings discovered by runZero researchers
2026-07-01: advisory: NVD publication date

References

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