#VU77254 Use-after-free in Linux kernel - CVE-2020-36694

Vulnerability identifier: #VU77254

Vulnerability risk: Low

CVSSv4.0: 5.7 [CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2020-36694

CWE-ID: CWE-416

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 escalate privileges on the system.

The vulnerability exists due to a use-after-free error in the packet processing context, because the per-CPU sequence count is mishandled during concurrent iptables rules replacement. A local user with CAP_NET_ADMIN capability in an unprivileged namespace can execute arbitrary code with elevated privileges.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Linux kernel: before 5.10, 5.12, 5.10

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External links
https://syzkaller.appspot.com/bug?id=0c4fd9c6aa04ec116d01e915d3b186f71a212cb2
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=cc00bcaa589914096edef7fb87ca5cee4a166b5c
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.12
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.10

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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.