#VU59100 Use-after-free in Linux kernel - CVE-2021-44733

Vulnerability identifier: #VU59100

Vulnerability risk: Low

CVSSv4.0: 7.1 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/U:Clear]

CVE-ID: CVE-2021-44733

CWE-ID: CWE-416

Exploitation vector: Local

Exploit availability: Yes

Vulnerable software:
Linux kernel
Operating systems & Components / Operating system

Vendor: Linux Foundation

Description

The vulnerability allows a local user to elevate privileges on the system.

The vulnerability exists due to a use-after-free error in the drivers/tee/tee_shm.c file within the TEE subsystem in the Linux kernel. A local user can trigger a race condition in tee_shm_get_from_id during an attempt to free a shared memory object and execute arbitrary code with elevated privileges.

Mitigation
Cybersecurity Help is currently unaware of any official solution to address this vulnerability.

Vulnerable software versions

Linux kernel: 5.15 rc1 - 5.15.11

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External links
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/drivers/tee/tee_shm.c
https://lore.kernel.org/lkml/20211215092501.1861229-1-jens.wiklander@linaro.org/
https://github.com/pjlantz/optee-qemu/blob/main/README.md

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Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.