CVE-2021-46904: Linux Kernel

Medium severity, CVSS 5.5. EPSS: 0.3% chance of exploitation in the next 30 days.

In the Linux kernel, the following vulnerability has been resolved: net: hso: fix null-ptr-deref during tty device unregistration Multiple ttys try to claim the same the minor number causing a double unregistration of the same device. The first unregistration succeeds but the next one results in a null-ptr-deref. The get_free_serial_index() function returns an available minor number but doesn't assign it immediately. The assignment is done by the caller later. But before this assignment, calls to get_free_serial_index() would return the same minor number. Fix this by modifying get_free_serial_index to assign the minor number immediately after one is found to be and rename it to obtain_minor() to better reflect what it does. Similary, rename set_serial_by_index() to release_minor() and modify it to free up the minor number of the given hso_serial. Every obtain_minor() should have corresponding release_minor() call.

Affected products

• Linux Linux Kernel: from 2.6.27, before 4.4.268 (fixed in 4.4.268); from 4.5.0, before 4.9.268 (fixed in 4.9.268); from 4.10.0, before 4.14.232 (fixed in 4.14.232); from 4.15.0, before 4.19.187 (fixed in 4.19.187); from 4.20.0, before 5.4.112 (fixed in 5.4.112); from 5.5.0, before 5.10.30 (fixed in 5.10.30); …

Published 2024-02-26. Last modified 2026-06-17.