#VU55261 Use-after-free in Linux kernel - CVE-2021-33033

Vulnerability identifier: #VU55261

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-2021-33033

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 improper handling of the CIPSO and CALIPSO refcounting for the DOI definitions in cipso_v4_genopt(0 function in net/ipv4/cipso_ipv4.c in Linux kernel. A local user can trigger a use-after-free error and execute arbitrary code with escalated privileges.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Linux kernel: before 5.11.4, 5.11.4

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External links
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ad5d07f4a9cd671233ae20983848874731102c08
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.14
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.7
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1165affd484889d4986cf3b724318935a0b120d8
https://sites.google.com/view/syzscope/kasan-use-after-free-read-in-cipso_v4_genopt
https://syzkaller.appspot.com/bug?id=96e7d345748d8814901c91cd92084ed04b46701e

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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.