CVE-2023-43615: Arm Mbed TLS Buffer Overflow Vulnerability

CVE-2023-43615 Overview

CVE-2023-43615 is a buffer overflow vulnerability affecting Mbed TLS, a popular open-source cryptographic library developed by Arm. The vulnerability exists in Mbed TLS versions 2.x before 2.28.5 and 3.x before 3.5.0. As a widely-used TLS implementation in embedded systems, IoT devices, and security-critical applications, this vulnerability poses significant risk to organizations relying on affected versions for secure communications.

Critical Impact

This buffer overflow vulnerability in Mbed TLS could allow remote attackers to potentially access sensitive information through network-based attacks without requiring authentication or user interaction.

Affected Products

• Arm Mbed TLS versions 2.x before 2.28.5
• Arm Mbed TLS versions 3.x before 3.5.0
• Fedora 37, 38, and 39 (packages containing affected Mbed TLS versions)

Discovery Timeline

• 2023-10-07 - CVE-2023-43615 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-43615

Vulnerability Analysis

This vulnerability is classified as CWE-120 (Buffer Copy without Checking Size of Input), commonly known as a classic buffer overflow. The flaw occurs when data is copied to a buffer without proper bounds checking, potentially allowing an attacker to write beyond the allocated memory boundaries. In the context of a TLS library like Mbed TLS, this type of vulnerability is particularly concerning as TLS operations process untrusted network data during cryptographic handshakes and data exchange.

The network-accessible nature of this vulnerability means that attackers can potentially exploit it remotely without requiring any privileges or user interaction, making it a significant concern for internet-facing systems utilizing affected Mbed TLS versions.

Root Cause

The root cause of CVE-2023-43615 stems from inadequate input validation when copying data into fixed-size buffers within the Mbed TLS codebase. Classic buffer overflow vulnerabilities like this one (CWE-120) typically occur when the library fails to verify that incoming data fits within the destination buffer's allocated size before performing the copy operation.

Attack Vector

The attack vector for this vulnerability is network-based. An attacker can potentially exploit this buffer overflow by sending specially crafted TLS traffic to a system running a vulnerable version of Mbed TLS. The exploitation does not require authentication or user interaction, making it accessible to remote attackers who can reach the target system over the network.

The buffer overflow could potentially be triggered during TLS handshake processing or other cryptographic operations where external data is parsed and processed by the library. Successful exploitation may allow attackers to read sensitive information from memory.

Detection Methods for CVE-2023-43615

Indicators of Compromise

• Unexpected crashes or segmentation faults in applications using Mbed TLS
• Anomalous TLS handshake failures or malformed TLS traffic patterns
• Memory corruption indicators in system logs from TLS-enabled services
• Unusual network traffic patterns targeting TLS-enabled endpoints

Detection Strategies

• Monitor applications using Mbed TLS for unexpected termination or memory-related errors
• Implement network intrusion detection rules to identify malformed TLS packets
• Use application security monitoring to detect buffer overflow exploitation attempts
• Conduct regular software composition analysis to identify affected Mbed TLS versions in your environment

Monitoring Recommendations

• Enable detailed logging for TLS-enabled applications and monitor for anomalous behavior
• Deploy memory protection mechanisms such as ASLR and stack canaries on systems running affected software
• Implement network traffic analysis to detect potential exploitation attempts against TLS services
• Monitor security advisories from Arm and distribution maintainers for updates

How to Mitigate CVE-2023-43615

Immediate Actions Required

• Update Mbed TLS to version 2.28.5 or later for the 2.x branch
• Update Mbed TLS to version 3.5.0 or later for the 3.x branch
• For Fedora users, apply the latest security updates via package management
• Inventory all systems and applications using Mbed TLS to ensure comprehensive patching

Patch Information

Arm has released patched versions of Mbed TLS that address this buffer overflow vulnerability. For detailed information about the fix, refer to the Mbed TLS Security Advisory. Fedora has also released updated packages for Fedora 37, 38, and 39 as documented in their package announcements.

Organizations should prioritize upgrading to Mbed TLS 2.28.5 or 3.5.0 depending on their current version branch. These patched versions include proper bounds checking to prevent the buffer overflow condition.

Workarounds

• Limit network exposure of systems running vulnerable Mbed TLS versions using firewalls and access controls
• Implement network segmentation to isolate systems that cannot be immediately patched
• Deploy Web Application Firewalls (WAF) or intrusion prevention systems to filter potentially malicious TLS traffic
• Monitor for vendor updates and apply patches as soon as they become available for your specific deployment

# Configuration example
# Check current Mbed TLS version on Linux systems
pkg-config --modversion mbedtls

# For systems using mbedtls package (Fedora/RHEL-based)
rpm -q mbedtls

# Update Mbed TLS via Fedora package manager
sudo dnf update mbedtls

# Verify updated version
rpm -q mbedtls