CVE-2023-45231: Tianocore EDK2 Information Disclosure Flaw

CVE-2023-45231 Overview

CVE-2023-45231 is an out-of-bounds read vulnerability affecting EDK2's Network Package. The flaw occurs when processing IPv6 Neighbor Discovery Redirect messages, allowing an attacker on an adjacent network to read memory beyond intended buffer boundaries. This vulnerability can be exploited to gain unauthorized access to sensitive information, potentially leading to a loss of confidentiality.

This vulnerability is part of a collection of flaws collectively known as "PixieFail," which affects the network stack in UEFI firmware implementations. EDK2 (EFI Development Kit II) is the open-source reference implementation of the UEFI specification, widely used across the industry in firmware for servers, workstations, and embedded systems.

Critical Impact

Attackers on an adjacent network can exploit this out-of-bounds read vulnerability to access sensitive memory contents, potentially exposing confidential data or aiding in further exploitation of the affected system.

Affected Products

• Tianocore EDK2 (all versions prior to security fix)
• Systems using EDK2-based UEFI firmware with IPv6 PXE boot enabled
• Enterprise servers and workstations with vulnerable network stack implementations

Discovery Timeline

• January 16, 2024 - CVE-2023-45231 published to NVD
• November 4, 2025 - Last updated in NVD database

Technical Details for CVE-2023-45231

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read). The flaw resides in EDK2's network stack implementation, specifically within the code responsible for parsing IPv6 Neighbor Discovery Protocol (NDP) Redirect messages. When the network stack receives a malformed or specially crafted Redirect message, it fails to properly validate the message boundaries before reading data, resulting in memory access beyond the allocated buffer.

The attack requires adjacent network access, meaning the attacker must be on the same network segment as the vulnerable system. No privileges or user interaction are required to exploit this vulnerability. While the vulnerability does not allow modification of data or cause denial of service directly, the information disclosure could expose sensitive memory contents that may facilitate further attacks.

Root Cause

The root cause of CVE-2023-45231 lies in insufficient bounds checking within the Neighbor Discovery Redirect message processing logic. When parsing the options field of an NDP Redirect message, the code does not adequately validate the length fields before reading option data. This allows a malicious actor to craft messages with incorrect length values that cause the parser to read beyond the message buffer into adjacent memory regions.

The vulnerability exists in the pre-boot environment during PXE network boot operations, where UEFI firmware processes network traffic to download boot images. This early-stage execution context means the vulnerability affects systems before the operating system's security controls are active.

Attack Vector

The attack vector for CVE-2023-45231 requires an attacker to have adjacent network access to the target system. The attack scenario typically involves:

1. The attacker positions themselves on the same network segment as the target system
2. The target system initiates a PXE boot or otherwise uses the vulnerable EDK2 network stack
3. The attacker sends crafted IPv6 Neighbor Discovery Redirect messages to the target
4. The vulnerable parsing code reads memory beyond the intended buffer boundaries
5. Sensitive memory contents are potentially exposed to the attacker through subsequent network responses or side-channel observations

The vulnerability mechanism involves improper handling of the Redirect message option parsing. When a Redirect message is received, the parsing function iterates through the options field. A malformed option with an incorrect length value can cause the parser to read data from memory locations outside the allocated buffer. For detailed technical information, see the GitHub Security Advisory and the PixieFail Proof of Concepts.

Detection Methods for CVE-2023-45231

Indicators of Compromise

• Unusual IPv6 Neighbor Discovery Redirect messages with malformed option length fields observed on the network
• Unexpected network traffic patterns during PXE boot operations
• Systems experiencing anomalous behavior during pre-boot network initialization
• Evidence of adjacent network reconnaissance targeting systems during boot sequences

Detection Strategies

• Deploy network monitoring to detect malformed IPv6 NDP Redirect messages with suspicious option lengths
• Monitor for unusual traffic patterns on PXE boot VLANs and network segments
• Implement deep packet inspection rules to identify PixieFail-related attack signatures
• Review UEFI firmware versions across infrastructure to identify vulnerable EDK2 implementations

Monitoring Recommendations

• Enable verbose logging on network switches for IPv6 NDP traffic in data center environments
• Configure IDS/IPS rules to alert on malformed Neighbor Discovery Protocol messages
• Monitor for unexpected PXE boot attempts from systems that should boot from local storage
• Establish baseline network behavior for pre-boot environments to detect anomalies

How to Mitigate CVE-2023-45231

Immediate Actions Required

• Update EDK2-based UEFI firmware to the latest patched version from your hardware vendor
• Disable IPv6 PXE boot functionality if not required for operations
• Isolate PXE boot networks and restrict access to trusted management systems only
• Review and apply vendor-specific firmware updates addressing the PixieFail vulnerabilities

Patch Information

Tianocore has released security updates to address this vulnerability. Organizations should obtain patched firmware from their respective hardware vendors, as EDK2 code is incorporated into vendor-specific firmware builds. Refer to the GitHub Security Advisory GHSA-hc6x-cw6p-gj7h for upstream patch details.

Additional vendor advisories:

• NetApp Security Advisory
• Fedora Package Announcement
• CERT Vulnerability Note VU#132380

Workarounds

• Disable IPv6 support in UEFI firmware if IPv6 PXE boot is not required
• Implement network segmentation to isolate PXE boot traffic from general network access
• Deploy network access controls to restrict which systems can send traffic to PXE boot segments
• Consider using IPv4-only PXE boot configurations until firmware updates are applied

# Example: Disable IPv6 PXE boot in UEFI settings (vendor-specific)
# Access UEFI setup utility during boot and navigate to:
# Network Stack Configuration -> IPv6 PXE Support -> Disabled
# 
# For systems using efibootmgr on Linux, review boot options:
efibootmgr -v | grep -i pxe
# 
# Network segmentation example - isolate PXE VLAN (switch configuration varies by vendor)
# Ensure PXE boot VLAN is only accessible from trusted management systems