CVE-2023-3090: Linux Kernel Privilege Escalation Flaw

CVE-2023-3090 Overview

A heap out-of-bounds write vulnerability exists in the Linux Kernel ipvlan network driver that can be exploited to achieve local privilege escalation. The vulnerability stems from missing skb->cb initialization in the ipvlan network driver, allowing attackers with local access to potentially escalate privileges on affected systems.

This memory corruption vulnerability is particularly concerning because it affects a core networking component of the Linux kernel. The ipvlan driver provides network virtualization capabilities and is commonly used in containerized environments, making this vulnerability relevant to cloud infrastructure and container deployments.

Critical Impact

Local attackers can exploit this heap out-of-bounds write to achieve privilege escalation, potentially gaining root access on vulnerable Linux systems with CONFIG_IPVLAN enabled.

Affected Products

• Linux Kernel (multiple versions with CONFIG_IPVLAN enabled)
• Debian Linux 10.0 (Buster)
• Debian Linux 11.0 (Bullseye)
• Debian Linux 12.0 (Bookworm)

Discovery Timeline

• June 28, 2023 - CVE-2023-3090 published to NVD
• February 13, 2025 - Last updated in NVD database

Technical Details for CVE-2023-3090

Vulnerability Analysis

The heap out-of-bounds write vulnerability in CVE-2023-3090 occurs within the Linux Kernel's ipvlan network driver due to improper memory initialization. The ipvlan driver is designed to provide network virtualization by allowing multiple virtual interfaces to share a single physical interface while maintaining isolation between them.

The core issue lies in the socket buffer control block (skb->cb) not being properly initialized before use. Socket buffers in the Linux kernel contain a control block area that drivers can use to store private data. When this area is not properly initialized, it may contain stale or malicious data from previous operations, leading to unpredictable behavior when the driver subsequently accesses this memory region.

The vulnerability is reachable when the kernel is compiled with CONFIG_IPVLAN enabled, which is a common configuration in systems that support container networking or network virtualization features.

Root Cause

The root cause of this vulnerability is missing initialization of the skb->cb (socket buffer control block) structure in the ipvlan network driver. When network packets are processed through the ipvlan driver, the control block memory may contain uninitialized or stale data from previous operations. This uninitialized memory is then used in subsequent operations, leading to a heap out-of-bounds write condition.

This class of vulnerability (CWE-787: Out-of-bounds Write) occurs when the software writes data past the end, or before the beginning, of the intended buffer. In this case, the uninitialized control block can cause the driver to write to incorrect memory locations during packet processing.

Attack Vector

Exploitation of CVE-2023-3090 requires local access to the vulnerable system. An attacker would need to:

1. Have local user access to a system running a vulnerable Linux kernel version
2. The target system must have CONFIG_IPVLAN enabled in the kernel configuration
3. Craft specific network operations that trigger the vulnerable code path in the ipvlan driver
4. Leverage the heap out-of-bounds write to corrupt kernel memory structures
5. Use the memory corruption to escalate privileges, potentially achieving root access

The vulnerability allows an attacker to achieve high impact on confidentiality, integrity, and availability of the affected system. Since this is a kernel-level vulnerability, successful exploitation could lead to complete system compromise.

The attack does not require any user interaction and has low complexity once the attacker has local access to the system.

Detection Methods for CVE-2023-3090

Indicators of Compromise

• Unexpected kernel crashes or panics related to ipvlan driver operations
• Anomalous privilege escalation events from low-privileged users
• Unusual network interface creation or manipulation activities involving ipvlan devices
• Kernel oops messages or memory corruption warnings in system logs referencing ipvlan

Detection Strategies

• Monitor kernel logs (dmesg, /var/log/kern.log) for ipvlan-related errors or memory corruption warnings
• Implement kernel integrity monitoring to detect unauthorized kernel memory modifications
• Deploy endpoint detection solutions capable of monitoring kernel-level activities and privilege changes
• Audit system calls related to network device creation and ipvlan interface manipulation

Monitoring Recommendations

• Enable kernel auditing for network namespace and interface operations
• Configure alerts for unexpected privilege escalation events or sudo/su activity from service accounts
• Monitor for processes attempting to create or manipulate ipvlan network interfaces
• Implement file integrity monitoring on kernel modules and driver files

How to Mitigate CVE-2023-3090

Immediate Actions Required

• Apply kernel patches that include commit 90cbed5247439a966b645b34eb0a2e037836ea8e immediately
• Review and restrict local user access to systems with ipvlan functionality enabled
• Consider disabling CONFIG_IPVLAN in kernel configuration if the feature is not required
• Monitor affected systems for signs of exploitation until patches are applied

Patch Information

The vulnerability has been addressed in the upstream Linux kernel through commit 90cbed5247439a966b645b34eb0a2e037836ea8e. This commit properly initializes the skb->cb structure in the ipvlan network driver, eliminating the out-of-bounds write condition.

Patches are available from multiple sources:

• Linux Kernel Git Repository Commit
• Debian Security Advisory DSA-5448
• Debian Security Advisory DSA-5480
• NetApp Security Advisory NTAP-20230731-0002

For Debian-based systems, apply updates using the standard package management tools. Kernel live patching is also available through solutions documented in the Packetstorm Security Notice LSN-0097 and LSN-0098.

Workarounds

• Disable ipvlan functionality by removing or blacklisting the ipvlan kernel module if not required
• Restrict local system access to trusted users only until patches can be applied
• Implement mandatory access controls (SELinux, AppArmor) to limit potential exploitation impact
• Use container security policies to restrict ipvlan network mode usage in containerized environments

# Check if ipvlan module is loaded
lsmod | grep ipvlan

# Blacklist ipvlan module to prevent loading (temporary workaround)
echo "blacklist ipvlan" | sudo tee /etc/modprobe.d/blacklist-ipvlan.conf

# Unload ipvlan module if currently loaded
sudo modprobe -r ipvlan

# Verify kernel version and check for patch
uname -r
# Update to patched kernel version
sudo apt update && sudo apt upgrade linux-image-$(uname -r)