SB20260720243 - Improper locking in Linux kernel bridge

Description

This security bulletin contains information about 1 vulnerability.

1) Improper locking (CVE-ID: CVE-2026-63988)

CWE-ID: CWE-667 - Improper Locking

CVSSv4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a local user to cause a denial of service.

The vulnerability exists due to improper lock management in brport_store() in the bridge sysfs interface when handling sysfs attribute writes that change bridge port flags and invoke dev_set_promiscuity(). A local user can write crafted values to affected bridge port sysfs attributes to cause a kernel BUG from sleeping in atomic context.

The issue affects non-STP bridge port attributes, while the STP-related path_cost and priority attributes are handled separately.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/2f9cb30d97e45686f3119fff3b30f12259950910
• https://git.kernel.org/stable/c/6d34594cc619d0d4b07d5afcad8b5984f3526dcf
• https://git.kernel.org/stable/c/e976e3f2f2005c6267089a1a3b6344f234a59a55