#VU90207 Use-after-free in Linux kernel - CVE-2021-47209

Vulnerability identifier: #VU90207

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-2021-47209

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 within the rq_of_rt_se() and rt_rq_of_se() functions in kernel/sched/rt.c, within the free_fair_sched_group() and unregister_fair_sched_group() functions in kernel/sched/fair.c, within the sched_free_group(), sched_online_group(), cpu_cgroup_css_released() and cpu_cgroup_css_free() functions in kernel/sched/core.c, within the autogroup_destroy() function in kernel/sched/autogroup.c. A local user can escalate privileges on the system.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Linux kernel: All versions

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External links
https://git.kernel.org/stable/c/512e21c150c1c3ee298852660f3a796e267e62ec
https://git.kernel.org/stable/c/b027789e5e50494c2325cc70c8642e7fd6059479

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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.