CVE-2022-1462: Linux Kernel Race Condition Vulnerability

CVE-2022-1462 Overview

CVE-2022-1462 is an out-of-bounds read vulnerability in the Linux kernel's TeleTYpe (TTY) subsystem. A local user can trigger a race condition through specific ioctl calls including TIOCSPTLCK, TIOCGPTPEER, TIOCSTI, and TCXONC. The race causes memory leakage in the flush_to_ldisc function. Successful exploitation allows a local attacker to crash the system or read unauthorized data from kernel memory. The vulnerability is classified as [CWE-362] Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition).

Critical Impact
Local attackers can leak kernel memory contents or induce a system crash by exploiting a race condition in TTY ioctl handling, leading to information disclosure and denial of service on affected Linux systems.

Affected Products

Linux Kernel (mainline)
Red Hat Enterprise Linux 8.0 and 9.0
Debian Linux 10.0

Discovery Timeline

2022-06-02 - CVE-2022-1462 published to the National Vulnerability Database (NVD)
2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-1462

Vulnerability Analysis

The flaw resides in the Linux kernel's TTY subsystem, which manages terminal devices and pseudo-terminal pairs. Concurrent invocation of specific ioctl operations creates a race window during line discipline buffer processing. The flush_to_ldisc function reads data outside the intended buffer boundaries when the race is won. This out-of-bounds read exposes adjacent kernel memory contents to user space or causes structural inconsistencies that crash the kernel.

The vulnerability requires local access and authenticated execution. While exploitation complexity is high due to the race condition timing, successful triggers expose sensitive kernel memory. Information disclosure from kernel space can include credentials, pointers useful for bypassing Kernel Address Space Layout Randomization (KASLR), or other security-sensitive data.

Root Cause

The root cause is improper synchronization between TTY ioctl handlers and the line discipline flush worker. The TIOCSPTLCK, TIOCGPTPEER, TIOCSTI, and TCXONC operations modify or read TTY state that flush_to_ldisc consumes asynchronously. Missing or insufficient locking allows flush_to_ldisc to operate on a stale or partially-modified buffer, producing an out-of-bounds read.

Attack Vector

A local user with the ability to open a pseudo-terminal can script repeated concurrent ioctl calls from multiple threads to win the race. The attacker does not need elevated privileges. Once the race is won, kernel memory is leaked back through the TTY data path or the kernel triggers a fault. Refer to the Red Hat Bug Report #2078466 and OSS Security Mailing List Post for the upstream technical discussion.

Detection Methods for CVE-2022-1462

Indicators of Compromise

Unexpected kernel oops or panic messages in dmesg referencing flush_to_ldisc or TTY line discipline functions
Processes performing high-frequency ioctl calls against /dev/ptmx or pseudo-terminal slave devices
Unprivileged processes consuming abnormal CPU while looping on TTY operations

Detection Strategies

Monitor kernel ring buffer logs for crashes and warnings originating in the TTY subsystem
Audit ioctl syscalls invoking TIOCSPTLCK, TIOCGPTPEER, TIOCSTI, and TCXONC from non-interactive or unexpected processes
Compare installed kernel package versions against vendor-published fixed releases

Monitoring Recommendations

Enable auditd rules covering ioctl operations on pseudo-terminal devices for sensitive systems
Forward kernel logs to a centralized logging platform and alert on TTY-related faults
Track CVE patch status across all Linux hosts through configuration management tooling

How to Mitigate CVE-2022-1462

Immediate Actions Required

Apply vendor-provided kernel updates from Red Hat, Debian, or your distribution as soon as available
Inventory all systems running affected kernel versions and prioritize patching for multi-user hosts
Restrict shell access on shared systems where untrusted local users could exploit the race

Patch Information

Fixes were issued through distribution maintainers. Refer to the Debian LTS Announcement and the Red Hat Bug Report #2078466 for fixed package versions. Reboot after kernel package installation to load the patched kernel.

Workarounds

Limit local user access on multi-tenant systems until patches are deployed
Use Linux Security Modules such as SELinux or AppArmor to constrain access to pseudo-terminal devices for low-trust accounts
Disable container workloads that grant unprivileged users access to /dev/ptmx where feasible

bash

# Verify the running kernel version and check for available updates
uname -r

# Red Hat / RHEL
sudo yum update kernel
sudo reboot

# Debian / Ubuntu
sudo apt-get update && sudo apt-get install --only-upgrade linux-image-$(uname -r)
sudo reboot