VDB-375556 · CVE-2026-6682 · EUVD-2026-40992

ChaN FatFs up to R0.16 mount_volume n_fats integer overflow

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
6.8	$0-$5k	0.00

Summaryinfo

A vulnerability was found in ChaN FatFs up to R0.16. It has been declared as critical. Impacted is the function mount_volume. Executing a manipulation of the argument n_fats can lead to integer overflow. This vulnerability is handled as CVE-2026-6682. The physical device can be targeted for the attack. There is not any exploit available.

Detailsinfo

A vulnerability has been found in ChaN FatFs up to R0.16 and classified as critical. This vulnerability affects the function mount_volume. The manipulation of the argument n_fats with an unknown input leads to a integer overflow vulnerability. The CWE definition for the vulnerability is CWE-190. The product performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In FatFS R0.16 and earlier contains a FAT32 integer overflow bug in mount_volume() where fasize *= fs->n_fats can wrap, leading to attacker-controlled file-size metadata and unsafe read lengths in downstream callers. This maps to CWE-190 (Integer Overflow or Wraparound). 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). Remote delivery is also possible in OTA/update pipelines. The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Total.

The weakness was released by Hd Moore. The advisory is shared for download at runzero.com. This vulnerability was named CVE-2026-6682 since 04/20/2026. The exploitation appears to be easy. The attack needs to be approached locally. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 07/01/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-40992). Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

ChaN

Name

FatFs

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.8
VulDB Meta Temp Score: 6.8

VulDB Base Score: 6.8
VulDB Temp Score: 6.8
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Integer overflow
CWE: CWE-190 / CWE-189
CAPEC: 🔒
ATT&CK: 🔒

Physical: Yes
Local: Yes
Remote: No

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

04/20/2026 CVE reserved
07/01/2026 +72 days Advisory disclosed
07/01/2026 +0 days VulDB entry created
07/01/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: runzero.com
Researcher: Hd Moore
Status: Not defined

CVE: CVE-2026-6682 (🔒)
GCVE (CVE): GCVE-0-2026-6682
GCVE (VulDB): GCVE-100-375556
EUVD: 🔒

Entryinfo

Created: 07/01/2026 17:14
Updated: 07/01/2026 19:27
Changes: 07/01/2026 17:14 (54), 07/01/2026 19:27 (1)
Complete: 🔍
Cache ID: 216::103