#VU93783 Incorrect calculation in Linux kernel - CVE-2020-29534

Vulnerability identifier: #VU93783

Vulnerability risk: Low

CVSSv4.0: 5.9 [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:U/U:Clear]

CVE-ID: CVE-2020-29534

CWE-ID: CWE-682

Exploitation vector: Local

Exploit availability: No

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

Vendor: Linux Foundation

Description

The vulnerability allows a local user to execute arbitrary code.

The vulnerability exists due to incorrect calculation within the __put_task_struct() and copy_process() functions in kernel/fork.c, within the __io_cqring_fill_event(), io_dismantle_req(), io_req_free_batch_finish(), io_req_free_batch(), io_close_prep(), io_req_drop_files(), io_req_set_file(), io_init_req(), io_submit_sqes(), io_sq_thread(), io_uring_alloc_task_context(), io_sq_offload_start(), io_wq_files_match(), io_uring_cancel_files(), io_cancel_task_cb(), SYSCALL_DEFINE6() and io_uring_get_fd() functions in fs/io_uring.c, within the exit_files() function in fs/file.c, within the bprm_execve() function in fs/exec.c. A local user can execute arbitrary code.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Linux kernel: All versions

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External links
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0f2122045b946241a9e549c2a76cea54fa58a7ff
https://bugs.chromium.org/p/project-zero/issues/detail?id=2089
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.9.3

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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.