SB20261023177 - Improper update of reference count in Linux kernel ksys_unshare() namespace cleanup in kernel/fork.c

Description

This security bulletin contains information about 1 vulnerability.

1) Improper update of reference count (CVE-ID: CVE-2026-98983)

CWE-ID: CWE-911 - Improper Update of Reference Count

CVSSv4: 2 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a local user to disrupt namespace tracking and cause active namespaces to disappear from listns() output.

The vulnerability exists due to improper reference count updates in ksys_unshare() when cleaning up an nsproxy that was never installed after set_cred_ucounts() fails. A local user can invoke unshare() under conditions where the caller's real UID differs from its effective UID and alloc_ucounts() cannot allocate to trigger incorrect namespace reference decrements and remove active namespaces from listns() output.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/0b6f31a3c0b16066f812e94b52a704174a6f23cd
• https://git.kernel.org/stable/c/56fe03a0c05dba4c5f6a23c391f96de1614a098c