#VU63385 Improper Validation of Array Index in Linux kernel - CVE-2021-43389

Vulnerability identifier: #VU63385

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-2021-43389

CWE-ID: CWE-129

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 with elevated privileges.

The vulnerability exists due to improper validation of array index in the ISDN CAPI implementation within detach_capi_ctr() function in drivers/isdn/capi/kcapi.c. A local user can send specially crafted data to the system and execute arbitrary code with elevated privileges.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Linux kernel: before 5.14.16, 5.14.16

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External links
https://lore.kernel.org/netdev/CAFcO6XOvGQrRTaTkaJ0p3zR7y7nrAWD79r48=L_BbOyrK9X-vA@mail.gmail.com/
https://seclists.org/oss-sec/2021/q4/39
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1f3e2e97c003f80c4b087092b225c8787ff91e4d
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.14.15
https://bugzilla.redhat.com/show_bug.cgi?id=2013180
https://www.openwall.com/lists/oss-security/2021/11/05/1
https://lists.debian.org/debian-lts-announce/2021/12/msg00012.html
https://www.debian.org/security/2022/dsa-5096
https://lists.debian.org/debian-lts-announce/2022/03/msg00012.html

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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.