CVE-2024-35887: ax25: fix use-after-free bugs caused by ax25_ds_del_timer

Vulnerability summary

CVE-2024-35887 is a high (CVSS 8.8) Use After Free vulnerability in linux. EPSS estimates a 0.34% chance of exploitation in the next 30 days, higher than 27.7% of scored vulnerabilities.

Timeline

1. 19-05-2024
   PublishedVulnerability first disclosed.
2. 14-09-2026
   Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: ax25: fix use-after-free bugs caused by ax25_ds_del_timer When the ax25 device is detaching, the ax25_dev_device_down() calls ax25_ds_del_timer() to cleanup the slave_timer. When the timer handler is running, the ax25_ds_del_timer() that calls del_timer() in it will return directly. As a result, the use-after-free bugs could happen, one of the scenarios is shown below: (Thread 1) | (Thread 2) | ax25_ds_timeout() ax25_dev_device_down() | ax25_ds_del_timer() | del_timer() | ax25_dev_put() //FREE | | ax25_dev-> //USE In order to mitigate bugs, when the device is detaching, use timer_shutdown_sync() to stop the timer.

• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.