Privilege escalation in tty subsystem in Linux kernel

1) Improper locking

EUVDB-ID: #VU51543

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-2020-29661

CWE-ID: CWE-667 - Improper Locking

Exploit availability: Yes

Description

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

The vulnerability exists due to locking error in the tty subsystem of the Linux kernel in drivers/tty/tty_jobctrl.c. An local user can exploit this vulnerability to trigger a use-after-free error against TIOCSPGRP and execute arbitrary code with elevated privileges.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Linux kernel: before

CPE2.3

• cpe:2.3:o:linux_foundation:linux_kernel:*:*:*:*:*:*:*:*

External links

https://packetstormsecurity.com/files/160681/Linux-TIOCSPGRP-Broken-Locking.html
https://www.openwall.com/lists/oss-security/2020/12/10/1
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=54ffccbf053b5b6ca4f6e45094b942fab92a25fc
https://lists.debian.org/debian-lts-announce/2021/02/msg00018.html
https://lists.debian.org/debian-lts-announce/2021/03/msg00010.html
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/BOB25SU6XUL4TNP7KB63WNZSYTIYFDPP/
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/MZ7OAKAEFAXQRGBZK4LYUWINCD3D2XCL/
https://security.netapp.com/advisory/ntap-20210122-0001/
https://www.debian.org/security/2021/dsa-4843

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.