SB2021111631 - Red Hat Enterprise Linux 7.4 Advanced Update Support update for kernel
Published: November 16, 2021
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 2 secuirty vulnerabilities.
1) Use-after-free (CVE-ID: CVE-2020-36385)
The vulnerability allows a local user to escalate privileges on the system.
The vulnerability exists due to a use-after-free error in drivers/infiniband/core/ucma.c, because the ctx is reached via the ctx_list in some ucma_migrate_id situations where ucma_close is called. A local user can run a specially crafted program to trigger the use-after-free error and execute arbitrary code with elevated privileges.
2) Security restrictions bypass (CVE-ID: CVE-2021-3653)
The vulnerability allows a malicious guest to escalate privileges on the system.
The vulnerability exists due to improperly imposed security restrictions within the KVM's AMD code for supporting SVM nested virtualization. The flaw occurs when processing the VMCB (virtual machine control block) provided by the L1 guest to spawn/handle a nested guest (L2). Due to improper validation of the "int_ctl" field, this issue could allow a malicious L1 to enable AVIC support (Advanced Virtual Interrupt Controller) for the L2 guest.
As a result, the L2 guest would be allowed to read/write physical pages of the host, resulting in a crash of the entire system, leak of sensitive data or potential guest-to-host escape.
Remediation
Install update from vendor's website.