Use-after-free in Linux kernel - CVE-2021-43057

Vulnerability identifier: #VU83427

CSH Severity: Low

CVSS v4: 8.5 [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]

CVE-ID: CVE-2021-43057

CWE-ID: CWE-416

Exploitation vector: Local access

Exploit availability: No public exploit available

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

The vulnerability exists due to a use-after-free error within the selinux_ptrace_traceme (aka the SELinux handler for PTRACE_TRACEME). A local authenticated user can trigger a use-after-free error and escalate privileges on the system.

Linux kernel
Ubuntu
linux-image-5.13.0-22-generic (Ubuntu package)
linux-image-5.13.0-22-generic-lpae (Ubuntu package)
linux-image-5.13.0-22-lowlatency (Ubuntu package)
linux-image-5.13.0-22-generic-64k (Ubuntu package)
linux-image-virtual (Ubuntu package)
linux-image-generic-64k (Ubuntu package)
linux-image-generic (Ubuntu package)
linux-image-lowlatency (Ubuntu package)
linux-image-generic-lpae (Ubuntu package)
linux-image-oem-20.04 (Ubuntu package)
linux-image-5.13.0-1006-kvm (Ubuntu package)
linux-image-kvm (Ubuntu package)
linux-image-gcp (Ubuntu package)
linux-image-gke (Ubuntu package)
linux-image-5.13.0-1007-aws (Ubuntu package)
linux-image-5.13.0-1007-gcp (Ubuntu package)
linux-image-aws (Ubuntu package)
linux-image-azure (Ubuntu package)
linux-image-5.13.0-1008-azure (Ubuntu package)
linux-image-oracle (Ubuntu package)
linux-image-5.13.0-1010-oracle (Ubuntu package)
linux-image-5.13.0-1011-raspi-nolpae (Ubuntu package)
linux-image-5.13.0-1011-raspi (Ubuntu package)
linux-image-raspi (Ubuntu package)
linux-image-raspi-nolpae (Ubuntu package)
linux-image-oem-20.04c (Ubuntu package)
linux-image-5.13.0-1020-oem (Ubuntu package)

Install update from vendor's website.

Linux kernel - update to 5.14.8
linux-image-5.13.0-22-generic (Ubuntu package) - update to 5.13.0-22.22
linux-image-5.13.0-22-generic-lpae (Ubuntu package) - update to 5.13.0-22.22
linux-image-5.13.0-22-lowlatency (Ubuntu package) - update to 5.13.0-22.22
linux-image-5.13.0-22-generic-64k (Ubuntu package) - update to 5.13.0-22.22
linux-image-virtual (Ubuntu package) - update to 5.13.0.22.33
linux-image-generic-64k (Ubuntu package) - update to 5.13.0.22.33
linux-image-generic (Ubuntu package) - update to 5.13.0.22.33
linux-image-lowlatency (Ubuntu package) - update to 5.13.0.22.33
linux-image-generic-lpae (Ubuntu package) - update to 5.13.0.22.33
linux-image-oem-20.04 (Ubuntu package) - update to 5.13.0.22.33
linux-image-5.13.0-1006-kvm (Ubuntu package) - update to 5.13.0-1006.6
linux-image-kvm (Ubuntu package) - update to 5.13.0.1006.6
linux-image-gcp (Ubuntu package) - update to 5.13.0.1007.8
linux-image-gke (Ubuntu package) - update to 5.13.0.1007.8
linux-image-5.13.0-1007-aws (Ubuntu package) - update to 5.13.0-1007.8
linux-image-5.13.0-1007-gcp (Ubuntu package) - update to 5.13.0-1007.8
linux-image-aws (Ubuntu package) - update to 5.13.0.1007.9
linux-image-azure (Ubuntu package) - update to 5.13.0.1008.9
linux-image-5.13.0-1008-azure (Ubuntu package) - update to 5.13.0-1008.9
linux-image-oracle (Ubuntu package) - update to 5.13.0.1010.12
linux-image-5.13.0-1010-oracle (Ubuntu package) - update to 5.13.0-1010.12
linux-image-5.13.0-1011-raspi-nolpae (Ubuntu package) - update to 5.13.0-1011.13
linux-image-5.13.0-1011-raspi (Ubuntu package) - update to 5.13.0-1011.13
linux-image-raspi (Ubuntu package) - update to 5.13.0.1011.17
linux-image-raspi-nolpae (Ubuntu package) - update to 5.13.0.1011.17
linux-image-oem-20.04c (Ubuntu package) - update to 5.13.0.1020.24
linux-image-5.13.0-1020-oem (Ubuntu package) - update to 5.13.0-1020.24

• https://bugs.chromium.org/p/project-zero/issues/detail?id=2229
• https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.14.8
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a3727a8bac0a9e77c70820655fd8715523ba3db7
• https://security.netapp.com/advisory/ntap-20211125-0001/

• Privilege escalation in Linux kernel PTRACE_TRACEME
• Ubuntu update for linux