Linux Kernel legacy_parse_param Heap Buffer Overflow Vulnerability (CVE-2022-0185) Technical Advisory
Executive & SecOps Summary
SECOPS ASSESSMENTLinux kernel versions 5.1 and lateral, specifically environments utilizing filesystems that fallback to legacy handling and have unprivileged user namespaces enabled
An unprivileged local attacker can trigger a heap-based buffer overflow in kernel memory, leading to local privilege escalation (LPE) to root
Apply the official kernel security patches immediately, or disable unprivileged user namespaces as a temporary workaround
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Update your Linux kernel to the latest patched version using the system package manager and reboot the host.
# For Ubuntu / Debian systems
sudo apt-get update && sudo apt-get install --only-upgrade -y linux-image-generic
sudo reboot
# For RHEL / Rocky Linux / AlmaLinux systems
sudo dnf clean all && sudo dnf update -y kernel
sudo reboot2. Temporary Workaround & Hardening Configuration
If patching and rebooting are not immediately feasible, mitigate the risk by disabling unprivileged user namespaces.
# Apply temporary mitigation immediately
sudo sysctl -w kernel.unprivileged_userns_clone=0
# Persist the configuration across reboots
echo 'kernel.unprivileged_userns_clone=0' | sudo tee -a /etc/sysctl.d/99-disable-sysctl.conf
sudo sysctl --system3. Log Audit & IoC Verification Commands
Verify the current running kernel version and check if unprivileged user namespaces are active on the system.
# Check current kernel version
uname -r
# Check status of unprivileged user namespaces (value of 0 indicates mitigated status)
sysctl kernel.unprivileged_userns_clone 2>/dev/null || cat /proc/sys/user/max_user_namespacesBlock Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
Protect unpatched Windows, Linux, and macOS workloads against in-memory exploitation and lateral movement with autonomous EDR.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2022-0185) is a heap-based buffer overflow flaw located in the legacy_parse_param function within the Filesystem Context functionality of the Linux kernel. Due to integer overflow (CWE-190) or underflow (CWE-191) during the validation of parameter lengths, the kernel fails to properly restrict the size of data copied into the allocated heap buffer, allowing out-of-bounds write operations.
2. Exploitation Mechanics & Attack Scenario
An attacker leverages filesystems that do not support the modern Filesystem Context API, forcing the kernel to fallback to legacy parameter parsing. If unprivileged user namespaces are enabled, a local user can create a new namespace to obtain containerized CAP_SYS_ADMIN privileges, which allows them to invoke the mount system call. By passing an excessively long parameter to legacy_parse_param, the attacker overflows the kernel heap, overwrites adjacent kernel structures, and hijacks the execution flow to escalate privileges to host root.
3. Infrastructure & Business Impact
As a high-severity vulnerability listed in the CISA KEV catalog, this flaw poses a severe threat to multi-tenant environments, container platforms (Kubernetes/Docker), and shared hosting servers. Successful exploitation allows complete container escape and full compromise of the underlying host infrastructure.
Official Vendor Advisories & References
A heap-based buffer overflow flaw was found in the way the legacy_parse_param function in the Filesystem Context functionality of the Linux kernel verified the supplied parameters length. An unprivileged (in case of unprivileged user namespaces enabled, otherwise needs namespaced CAP_SYS_ADMIN privilege) local user able to open a filesystem that does not support the Filesystem Context API (and thus fallbacks to legacy handling) could use this flaw to escalate their privileges on the system.
Frequently Asked SecOps Questions (CVE-2022-0185)
FAQQ1. How critical is CVE-2022-0185 and is it actively exploited in the wild?
CVE-2022-0185 is rated CVSS 8.4 (HIGH) with a 30-day EPSS exploitation probability of 25.1%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2022-0185?
Primary impacted vendors include linux across linux_kernel. Scope summary: Linux kernel versions 5.1 and newer prior to the patched releases, especially on systems with unprivileged user namespaces enabled
Q3. What temporary mitigations or workarounds exist for CVE-2022-0185 before patching?
[Mitigation] Apply the official kernel security patches immediately, or disable unprivileged user namespaces as a temporary workaround Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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