Use after free in Linux kernel - CVE-2021-28691

Vulnerability identifier: #VU95679

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-2021-28691

CWE-ID: CWE-416

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to execute arbitrary code.

Guest triggered use-after-free in Linux xen-netback A malicious or buggy network PV frontend can force Linux netback to disable the interface and terminate the receive kernel thread associated with queue 0 in response to the frontend sending a malformed packet. Such kernel thread termination will lead to a use-after-free in Linux netback when the backend is destroyed, as the kernel thread associated with queue 0 will have already exited and thus the call to kthread_stop will be performed against a stale pointer.

Linux kernel
Ubuntu
linux-image-5.8.0-1038-oracle (Ubuntu package)
linux-image-oracle (Ubuntu package)
linux-image-gcp (Ubuntu package)
linux-image-5.8.0-1039-gcp (Ubuntu package)
linux-image-5.8.0-1040-azure (Ubuntu package)
linux-image-azure (Ubuntu package)
linux-image-5.8.0-1042-aws (Ubuntu package)
linux-image-aws (Ubuntu package)
linux-image-oem-20.04 (Ubuntu package)
linux-image-oem-20.04b (Ubuntu package)
linux-image-5.10.0-1038-oem (Ubuntu package)
linux-image-5.11.0-27-generic-lpae (Ubuntu package)
linux-image-5.11.0-27-lowlatency (Ubuntu package)
linux-image-5.11.0-27-generic (Ubuntu package)
linux-image-5.11.0-27-generic-64k (Ubuntu package)
linux-image-lowlatency-hwe-20.04 (Ubuntu package)
linux-image-generic-64k-hwe-20.04 (Ubuntu package)
linux-image-virtual-hwe-20.04 (Ubuntu package)
linux-image-generic-lpae-hwe-20.04 (Ubuntu package)
linux-image-generic-hwe-20.04 (Ubuntu package)
linux-image-generic (Ubuntu package)
linux-image-lowlatency (Ubuntu package)
linux-image-generic-64k (Ubuntu package)
linux-image-virtual (Ubuntu package)
linux-image-5.11.0-31-generic (Ubuntu package)
linux-image-5.11.0-31-generic-lpae (Ubuntu package)
linux-image-generic-lpae (Ubuntu package)
linux-image-5.11.0-31-generic-64k (Ubuntu package)
linux-image-5.11.0-31-lowlatency (Ubuntu package)
linux-image-5.11.0-1013-azure (Ubuntu package)
linux-image-kvm (Ubuntu package)
linux-image-5.11.0-1014-kvm (Ubuntu package)
linux-image-raspi-nolpae (Ubuntu package)
linux-image-raspi (Ubuntu package)
linux-image-5.11.0-1016-raspi (Ubuntu package)
linux-image-5.11.0-1016-aws (Ubuntu package)
linux-image-5.11.0-1016-raspi-nolpae (Ubuntu package)
linux-image-5.11.0-1016-oracle (Ubuntu package)
linux-image-gke (Ubuntu package)
linux-image-5.11.0-1017-gcp (Ubuntu package)

Install update from vendor's repository.

linux-image-5.8.0-1038-oracle (Ubuntu package) - update to 5.8.0-1038.39~20.04.1
linux-image-oracle (Ubuntu package) - addressed in versions 5.8.0.1038.39~20.04.14, 5.11.0.1016.17
linux-image-gcp (Ubuntu package) - addressed in versions 5.8.0.1039.14, 5.11.0.1017.17
linux-image-5.8.0-1039-gcp (Ubuntu package) - update to 5.8.0-1039.41
linux-image-5.8.0-1040-azure (Ubuntu package) - update to 5.8.0-1040.43~20.04.1
linux-image-azure (Ubuntu package) - addressed in versions 5.8.0.1040.43~20.04.12, 5.11.0.1013.14
linux-image-5.8.0-1042-aws (Ubuntu package) - update to 5.8.0-1042.44~20.04.1
linux-image-aws (Ubuntu package) - addressed in versions 5.8.0.1042.44~20.04.14, 5.11.0.1016.17
linux-image-oem-20.04 (Ubuntu package) - addressed in versions 5.10.0.1038.40, 5.11.0.31.33
linux-image-oem-20.04b (Ubuntu package) - update to 5.10.0.1038.40
linux-image-5.10.0-1038-oem (Ubuntu package) - update to 5.10.0-1038.40
linux-image-5.11.0-27-generic-lpae (Ubuntu package) - update to 5.11.0-27.29~20.04.1
linux-image-5.11.0-27-lowlatency (Ubuntu package) - update to 5.11.0-27.29~20.04.1
linux-image-5.11.0-27-generic (Ubuntu package) - update to 5.11.0-27.29~20.04.1
linux-image-5.11.0-27-generic-64k (Ubuntu package) - update to 5.11.0-27.29~20.04.1
linux-image-lowlatency-hwe-20.04 (Ubuntu package) - update to 5.11.0.27.29~20.04.11
linux-image-generic-64k-hwe-20.04 (Ubuntu package) - update to 5.11.0.27.29~20.04.11
linux-image-virtual-hwe-20.04 (Ubuntu package) - update to 5.11.0.27.29~20.04.11
linux-image-generic-lpae-hwe-20.04 (Ubuntu package) - update to 5.11.0.27.29~20.04.11
linux-image-generic-hwe-20.04 (Ubuntu package) - update to 5.11.0.27.29~20.04.11
linux-image-generic (Ubuntu package) - update to 5.11.0.31.33
linux-image-lowlatency (Ubuntu package) - update to 5.11.0.31.33
linux-image-generic-64k (Ubuntu package) - update to 5.11.0.31.33
linux-image-virtual (Ubuntu package) - update to 5.11.0.31.33
linux-image-5.11.0-31-generic (Ubuntu package) - update to 5.11.0-31.33
linux-image-5.11.0-31-generic-lpae (Ubuntu package) - update to 5.11.0-31.33
linux-image-generic-lpae (Ubuntu package) - update to 5.11.0.31.33
linux-image-5.11.0-31-generic-64k (Ubuntu package) - update to 5.11.0-31.33
linux-image-5.11.0-31-lowlatency (Ubuntu package) - update to 5.11.0-31.33
linux-image-5.11.0-1013-azure (Ubuntu package) - update to 5.11.0-1013.14
linux-image-kvm (Ubuntu package) - update to 5.11.0.1014.15
linux-image-5.11.0-1014-kvm (Ubuntu package) - update to 5.11.0-1014.15
linux-image-raspi-nolpae (Ubuntu package) - update to 5.11.0.1016.14
linux-image-raspi (Ubuntu package) - update to 5.11.0.1016.14
linux-image-5.11.0-1016-raspi (Ubuntu package) - update to 5.11.0-1016.17
linux-image-5.11.0-1016-aws (Ubuntu package) - update to 5.11.0-1016.17
linux-image-5.11.0-1016-raspi-nolpae (Ubuntu package) - update to 5.11.0-1016.17
linux-image-5.11.0-1016-oracle (Ubuntu package) - update to 5.11.0-1016.17
linux-image-gke (Ubuntu package) - update to 5.11.0.1017.17
linux-image-5.11.0-1017-gcp (Ubuntu package) - update to 5.11.0-1017.19

• https://xenbits.xenproject.org/xsa/advisory-374.txt
• https://security.gentoo.org/glsa/202107-30
• https://security.netapp.com/advisory/ntap-20210805-0002/

• Use after free in Linux kernel
• Ubuntu update for linux-oem-5.10
• Ubuntu update for linux
• Ubuntu update for linux-aws-5.8