CVE-2023-23586: Use after free in io_uring in the Linux Kernel

Vulnerability summary

CVE-2023-23586 is a medium (CVSS 5.5) Use After Free vulnerability in linux linux_kernel. EPSS estimates a 0.27% chance of exploitation in the next 30 days, higher than 18.9% of scored vulnerabilities.

Timeline

1. 17-02-2023
   PublishedVulnerability first disclosed.
2. 12-03-2025
   Last modifiedVulnerability information updated.

Description

Due to a vulnerability in the io_uring subsystem, it is possible to leak kernel memory information to the user process. timens_install calls current_is_single_threaded to determine if the current process is single-threaded, but this call does not consider io_uring's io_worker threads, thus it is possible to insert a time namespace's vvar page to process's memory space via a page fault. When this time namespace is destroyed, the vvar page is also freed, but not removed from the process' memory, and a next page allocated by the kernel will be still available from the user-space process and can leak memory contents via this (read-only) use-after-free vulnerability. We recommend upgrading past version 5.10.161 or commit  788d0824269bef539fe31a785b1517882eafed93 https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/io_uring

• 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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.