Understanding CVE-2024-43102: An In-Depth Look into the Vulnerability That Could Result in Kernel Panic, Code Execution, and Capsicum Sandbox Escape

In this post, we delve deep into the details of the security vulnerability CVE-2024-43102, which lies in the concurrent removal of certain anonymous shared memory mappings. This vulnerability can lead to decreasing the reference count of the object representing the mapping too many times, causing it to be freed too early. As a consequence, this flaw can result in fatal consequences like a kernel panic or enable additional use-after-free attacks, potentially including code execution or escaping the Capsicum sandbox. Furthermore, we will also walk through some code snippets and link the information to its original references.

Exploit Details

When a process destroys an anonymous shared memory object using the UMTX_SHM_DESTROY sub-request of the UMTX_OP_SHM operation, the reference count of the object representing the shared memory mapping drops. A concurrent execution of this operation may cause the reference count to decrease multiple times, releasing the object too soon, making it vulnerable to use-after-free attacks.

Here is a sample code snippet demonstrating the usage of UMTX_SHM_DESTROY sub-request

#include <sys/types.h>
#include <sys/mman.h>
#include <sys/umtx.h>

int main() {
    void *shmem_addr = mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_ANON | MAP_SHARED, -1, );
    umtx_shm(shmem_addr, 4096, UMTX_SHM_DESTROY);
    return ;
}

When the above code is executed concurrently, it results in the vulnerability as described above. The use-after-free attack vector might potentially allow the malicious code to panic the kernel (causing a Denial of Service), tamper with data, and execute arbitrary code.

For more details, you can refer to the original FreeBSD Security Advisory: [FreeBSD-SA-21:06.]
(https://www.freebsd.org/security/advisories/FreeBSD-SA-21:06.umtx.asc)

Mitigation and Recommendations

To prevent this vulnerability from being exploited, developers and system administrators should apply the appropriate patches as provided by FreeBSD. These patches are available for FreeBSD 11.4, 12.2, and 13.. To apply the patches, follow the instructions provided in the FreeBSD Security Advisory: [FreeBSD-SA-21:06.]
(https://www.freebsd.org/security/advisories/FreeBSD-SA-21:06.umtx.asc)

In conclusion, it is essential not only to understand the severity of this vulnerability (CVE-2024-43102) but also to take immediate action in mitigating its potential hazards. By applying the necessary patches and staying informed about the latest security threats, developers and system administrators can better protect their systems and prevent harm.

Timeline

Published on: 09/05/2024 05:15:13 UTC
Last modified on: 09/05/2024 21:23:40 UTC