# CVE-2026-19669: Zephyr fuel gauge syscall stack buffer overflow

Source: https://junglewise.ai/threats/cve-2026-19669-the-user-mode-syscall-verifiers-z-vrfy-fuel-gauge-get-props-and-z  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-11. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-19669 · Severity: high · CVSS 7.8 · Published 2026-10-11

Zephyr's fuel gauge driver contains a privilege escalation flaw in syscall handlers that validate user-supplied requests. An attacker in user mode can provide an arbitrarily large array size to trigger allocation of oversized buffers on the privileged kernel stack, leading to out-of-bounds writes with attacker-controlled data. This breaks the sandbox isolation between user and kernel mode, allowing arbitrary code execution with kernel privileges.

Technologies: [Zephyr RTOS](https://junglewise.ai/threats/technologies/rtos). Vendors: [Zephyr](https://junglewise.ai/threats/vendors/zephyr).

## Quick answers

**Is CVE-2026-19669 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-19669 being exploited in the wild.

**How severe is CVE-2026-19669?** High severity, with a CVSS score of 7.8, published 11 October 2026.

**Which products and versions are affected?** Zephyr RTOS affected versions not specified in advisory.

**Is there a fix for CVE-2026-19669?** 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-2026-19669 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2026-19669?** Check whether you run Zephyr RTOS 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

The z_vrfy_fuel_gauge_get_props() and z_vrfy_fuel_gauge_set_props() syscall verifiers in drivers/fuel_gauge/fuel_gauge_syscall_handlers.c allocate variable-length arrays (VLAs) sized directly by an unvalidated caller-supplied len parameter, bypassing bounds checks and permission validation. The subsequent k_usermode_from_copy() call memcpy's attacker-controlled data without validating the destination bounds. Any thread with CONFIG_USERSPACE enabled can trigger a stack buffer overflow on the privileged stack; threads with fuel-gauge device permissions can additionally write fully attacker-controlled content.

## Affected products

- Zephyr Zephyr RTOS affected versions not specified in advisory

## Timeline

- 2026-10-11: disclosed

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