CVE-2023-4622

A use-after-free vulnerability in the Linux kernels af_unix component can be exploited to achieve local privilege escalation.

The unix_stream_sendpage() function tries to add data to the last skb in the peers recv queue without locking the queue. Thus there is a race where unix_stream_sendpage() could access an skb locklessly that is being released by garbage collection, resulting in use-after-free.

We recommend upgrading past commit 790c2f9d15b594350ae9bca7b236f2b1859de02c.

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

• http://packetstormsecurity.com/files/175963/Kernel-Live-Patch-Security-Notice-LSN-0099-1.html
• https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-6.1.y\u0026id=790c2f9d15b594350ae9bca7b236f2b1859de02c
• https://kernel.dance/790c2f9d15b594350ae9bca7b236f2b1859de02c
• https://lists.debian.org/debian-lts-announce/2023/10/msg00027.html
• https://lists.debian.org/debian-lts-announce/2024/01/msg00004.html
• https://www.debian.org/security/2023/dsa-5492