CVE-2023-6546: Kernel: gsm multiplexing race condition leads to privilege escalation

Severity: high (CVSS 7.0 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-12-21 · updated 2026-08-06
Weakness: CWE-366

Description

A race condition was found in the GSM 0710 tty multiplexor in the Linux kernel. This issue occurs when two threads execute the GSMIOC_SETCONF ioctl on the same tty file descriptor with the gsm line discipline enabled, and can lead to a use-after-free problem on a struct gsm_dlci while restarting the gsm mux. This could allow a local unprivileged user to escalate their privileges on the system.

Affected products

Fedoraproject Fedora: 39
Linux kernel: before 6.5; 6.5-rc1, 6.5-rc2, 6.5-rc3, 6.5-rc4, 6.5-rc5, 6.5-rc6 — fixed in 6.5
Red Hat Enterprise Linux: 8.0, 9.0

How to fix

Upgrade to a fixed version: Linux kernel 6.5. Check the vendor advisory for mitigations.

References

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