Cloudanix VulnDB

CVE-2026-98883

None

CVSS

—

EPSS

0.2%

Published

Oct 23, 2026

CISA due date

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Cloudanix analysis

Schedule a fix SSVC: Track

A small bug in the Linux kernel caused unnecessary warning messages on certain specialized MIPS hardware during startup, which is now fixed by a simple code update.

Exploitation
Other
Attacker needs
Local User
Complexity
Theoretical
Impact
Denial Of Service
Component
OS kernel
Class
Improper Input Validation
Remediation
Patch
Effort
Low
Patch risk
Low

What it actually does

The kernel's 8250 serial driver lacks handling for UPIO_AU (UART type 4) in set_io_from_upio, emitting a warning and failing to recognize valid Alchemy platform configuration during probe.

Why it matters to the business

MIPS Alchemy-based embedded devices may log spurious warnings at boot or experience delayed or incomplete serial port initialization, potentially impacting console access and device reliability in specialized hardware deployments.

How an attack unfolds

An attacker with local access could trigger repeated 8250 port registration on an affected Alchemy system to generate noise in logs or interfere with serial initialization, though no remote code execution or privilege escalation path exists.

How to fix it

Update to a Linux kernel version that includes the fix recognizing UPIO_AU in set_io_from_upio; no configuration changes required as the change is contained within the driver.

How to confirm the fix worked

After patching, confirm absence of the 'Unsupported UART type 4' warning during 8250 probe on Alchemy hardware and verify successful serial port registration without fallback errors.

Typical attack path

  1. Obtain local shell or physical access to target MIPS Alchemy platform
  2. Trigger 8250 serial driver probe via module load or device registration
  3. Observe warning and unsupported type handling failure in set_io_from_upio

How to detect it

Review kernel boot and dmesg logs for the exact warning string referencing set_io_from_upio and unsupported UART type 4 on systems using the 8250 driver with Alchemy platforms.

  • WARNING: drivers/tty/serial/8250/8250_port.c:462 at set_io_from_upio
  • Unsupported UART type 4

What your security team should do

  • Prioritize patching on any MIPS Alchemy or Au1300-based systems within the next maintenance window
  • Monitor kernel boot logs for serial driver warnings on affected hardware
  • Apply the upstream commit that adds UPIO_AU recognition to prevent unnecessary noise

The record

In the Linux kernel, the following vulnerability has been resolved: serial: 8250_port: recognize UPIO_AU My MIPS Alchemy systems generate the following warning during probe of the 8250 driver: WARNING: drivers/tty/serial/8250/8250_port.c:462 at set_io_from_upio+0xfc/0x124, CPU#0: swapper/0/1 Unsupported UART type 4 [...] [<80521d40>] set_io_from_upio+0xfc/0x124 [<80521dfc>] serial8250_set_defaults+0x94/0xe0 [<80520fb4>] serial8250_register_8250_port+0x288/0x51c [<805214ec>] serial8250_probe+0x160/0x1e8 [<8053b5f0>] platform_probe+0x64/0x90 The least invasive fix is to recognize UPIO_AU (type 4) in set_io_from_upio() and do nothing, since all parameters have already been set up in 8250_rt288x.c::au_platform_setup(). Run-tested on Alchemy Au1300 platform.

Affected packages

Ecosystem Package Introduced Fixed