CVE-2021-47356: In the Linux kernel, the following vulnerability has been resolved: mISDN: fix possible use-after-free in HFC_cleanup() This module's remove path ca...

Description

In the Linux kernel, the following vulnerability has been resolved: mISDN: fix possible use-after-free in HFC_cleanup() This module's remove path calls del_timer(). However, that function does not wait until the timer handler finishes. This means that the timer handler may still be running after the driver's remove function has finished, which would result in a use-after-free. Fix by calling del_timer_sync(), which makes sure the timer handler has finished, and unable to re-schedule itself.

Metrics

CVSS 3.1

7.7/10

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

EPSS Probability

0.27%

18.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-416

Affected Software

Vendor	Product	Versions
Linux	Linux Kernel	< 4.4.276
Linux	Linux Kernel	>= 4.5, < 4.9.276
Linux	Linux Kernel	>= 4.10, < 4.14.240
Linux	Linux Kernel	>= 4.15, < 4.19.198
Linux	Linux Kernel	>= 4.20, < 5.4.133
Linux	Linux Kernel	>= 5.5, < 5.10.51
Linux	Linux Kernel	>= 5.11, < 5.12.18
Linux	Linux Kernel	>= 5.13, < 5.13.3

References

Timeline

Published: May 21, 2024
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2021-47356?

In the Linux kernel, the following vulnerability has been resolved: mISDN: fix possible use-after-free in HFC_cleanup() This module's remove path calls del_timer(). However, that function does not wait until the timer handler finishes. This means that the timer handler may still be running after the driver's remove function has finished, which would result in a use-after-free. Fix by calling del_timer_sync(), which makes sure the timer handler has finished, and unable to re-schedule itself.

How severe is CVE-2021-47356?

CVE-2021-47356 has a CVSS score of 7.7/10 (HIGH severity). The EPSS model estimates a 0.27% probability of exploitation in the next 30 days.

How do I fix CVE-2021-47356?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.