CVE-2026-90834

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Source

https://cve.org/CVERecord?id=CVE-2026-90834

Import Source

https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90834.json

JSON Data

https://api.osv.dev/v1/vulns/CVE-2026-90834

Aliases

GHSA-xvwx-ww79-r346

Published

2026-11-10T22:07:45Z

Modified

2026-11-11T13:26:41Z

Severity

5.5 (Medium) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CVSS Calculator

Summary

UART wide-data syscall verifiers check the 8-bit driver op, allowing a user-mode thread to trigger a NULL function-pointer call in kernel mode

Details

The user-mode syscall verifiers for the 16-bit ("wide data") UART API in drivers/serial/uart_handlers.c validated the wrong driver operation. z_vrfy_uart_poll_out_u16(), z_vrfy_uart_tx_u16() and z_vrfy_uart_rx_enable_u16() each ran K_SYSCALL_DRIVER_UART() against the 8-bit op (poll_out, tx, rx_enable) rather than the 16-bit op that the corresponding implementation dereferences (poll_out_u16, tx_u16, rx_enable_u16). z_impl_uart_poll_out_u16(), z_impl_uart_tx_u16() and z_impl_uart_rx_enable_u16() in include/zephyr/drivers/uart/uart_internal.h call their op unconditionally, with no NULL guard of their own, because the verifier is supposed to have established that the op exists.

CONFIG_UART_WIDE_DATA is an application-selectable option that no driver selects, and only a handful of the serial drivers in the tree implement any _u16 operation; every other driver leaves those struct uart_driver_api members NULL while still providing the 8-bit ops the old check inspected. In a build with CONFIG_USERSPACE and CONFIG_UART_WIDE_DATA (plus CONFIG_UART_ASYNC_API for the uart_tx_u16() and uart_rx_enable_u16() variants), an unprivileged user-mode thread that legitimately holds access to such a UART device object can invoke the _u16 syscall: the object, permission and op checks all pass, and the kernel-side implementation then performs an indirect call through a NULL function pointer while running at supervisor privilege.

The result is a CPU exception taken in kernel context instead of the intended K_OOPS or -ENOSYS return. With the default k_sys_fatal_error_handler() this halts the system (or warm-reboots it under CONFIG_RESET_ON_FATAL_ERROR), so a thread confined by the userspace sandbox can deny service to the whole device — a capability the user-mode privilege boundary is specifically meant to withhold. The call target is a fixed NULL, so there is no attacker-controlled code execution and no memory disclosure; the separate K_SYSCALL_MEMORY_ARRAY_READ()/K_SYSCALL_MEMORY_ARRAY_WRITE() bounds checks on the caller's buffer were and remain correct. The fix points each verifier at the matching _u16 op, using a plain K_SYSCALL_OBJ() object check where the op does not exist or where the implementation already tests it for NULL.

Database specific

{
    "cna_assigner": "zephyr",
    "cwe_ids": [
        "CWE-476"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90834.json"
}

References

Affected packages

Git / github.com/zephyrproject-rtos/zephyr

Affected ranges

Type

GIT

Repo

https://github.com/zephyrproject-rtos/zephyr

Events

Introduced

4f8d78ceeb436e82f528511998515f6fc137c6cd

Fixed

28af05ca658cbacf745fd5b099566311c58ccb1d

Introduced

684c9e8f32e4373a21098559f748f06915f950c9

Fixed

41d10b59730406bbab4ca9f1fbbe9e96aafb4966

Fixed

3c13bfd3d3ccdceeb51b884fed5a8d2a49475484

Database specific

Show details

{
    "extracted_events": [
        {
            "range": [
                {
                    "introduced": "3.0.0"
                },
                {
                    "fixed": "4.3.2"
                }
            ],
            "source": "AFFECTED_FIELD",
            "strategy": "StandardRange"
        },
        {
            "range": [
                {
                    "introduced": "4.4.0"
                },
                {
                    "fixed": "4.5.0"
                }
            ],
            "source": "AFFECTED_FIELD",
            "strategy": "StandardRange"
        },
        {
            "range": [
                {
                    "fixed": "3c13bfd3d3ccdceeb51b884fed5a8d2a49475484"
                }
            ],
            "source": "REFERENCES_COMMIT"
        }
    ]
}

Affected versions

v3.*

v3.0.0

v3.1.0

v3.1.0-rc1

v3.1.0-rc2

v3.1.0-rc3

v3.2.0

v3.2.0-rc1

v3.2.0-rc2

v3.2.0-rc3

v3.3.0

v3.3.0-rc1

v3.3.0-rc2

v3.3.0-rc3

v3.4.0

v3.4.0-rc1

v3.4.0-rc2

v3.4.0-rc3

v3.5.0

v3.5.0-rc1

v3.5.0-rc2

v3.5.0-rc3

v3.6.0

v3.6.0-rc1

v3.6.0-rc2

v3.6.0-rc3

v3.7.0

v3.7.0-rc1

v3.7.0-rc2

v3.7.0-rc3

v4.*

v4.0.0

v4.0.0-rc1

v4.0.0-rc2

v4.0.0-rc3

v4.1.0

v4.1.0-rc1

v4.1.0-rc2

v4.1.0-rc3

v4.2.0

v4.2.0-rc1

v4.2.0-rc2

v4.2.0-rc3

v4.3.0

v4.3.0-rc1

v4.3.0-rc2

v4.3.0-rc3

v4.3.1

v4.3.1-rc1

v4.4.0

zephyr-v3.*

zephyr-v3.0.0

zephyr-v3.1.0

zephyr-v3.2.0

zephyr-v3.3.0

zephyr-v3.4.0

zephyr-v3.5.0

Database specific

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90834.json"

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vanir_signatures_modified

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