CVE-2024-49195: Arm Mbed TLS Buffer Overflow Vulnerability

CVE-2024-49195 Overview

CVE-2024-49195 is a buffer underrun vulnerability in Mbed TLS versions 3.5.x through 3.6.x before 3.6.2. The flaw occurs in the pkwrite module when writing an opaque key pair, potentially allowing attackers to corrupt memory and achieve arbitrary code execution or cause denial of service conditions.

Critical Impact

This buffer underrun vulnerability in Mbed TLS's cryptographic key handling could enable remote attackers to corrupt memory, potentially leading to complete system compromise in applications relying on this widely-used TLS library.

Affected Products

• Arm Mbed TLS versions 3.5.x through 3.5.x
• Arm Mbed TLS versions 3.6.x before 3.6.2
• Any application or embedded system using affected Mbed TLS versions

Discovery Timeline

• October 15, 2024 - CVE-2024-49195 published to NVD
• May 6, 2025 - Last updated in NVD database

Technical Details for CVE-2024-49195

Vulnerability Analysis

This vulnerability is classified under CWE-787 (Out-of-Bounds Write), manifesting as a buffer underrun condition in the pkwrite component of Mbed TLS. The flaw occurs when the library attempts to write opaque key pair data, where improper boundary calculations result in memory writes occurring before the allocated buffer's starting address.

Buffer underrun vulnerabilities are particularly dangerous in cryptographic libraries because they can corrupt adjacent memory structures, potentially exposing sensitive cryptographic material or allowing attackers to manipulate program execution flow. In the context of Mbed TLS, which is widely deployed in embedded systems, IoT devices, and security-critical applications, this vulnerability poses significant risks to infrastructure relying on TLS/SSL communications.

Root Cause

The root cause lies in the pkwrite module's handling of opaque key pairs. When serializing these cryptographic objects, the code incorrectly calculates buffer offsets, resulting in write operations that precede the intended memory region. This type of arithmetic error in pointer manipulation or length calculations can occur when negative offsets are used without proper bounds validation, or when buffer size assumptions do not account for all key format variations.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker could potentially trigger this vulnerability by:

1. Providing maliciously crafted key data during TLS handshake operations
2. Exploiting applications that import or process external cryptographic keys using affected Mbed TLS functions
3. Targeting services that handle opaque key operations in PSA Crypto API contexts

The network-accessible nature combined with no required privileges makes this vulnerability particularly severe for internet-facing services using affected Mbed TLS versions.

The vulnerability manifests during opaque key pair write operations in the pkwrite module. When the library processes certain key formats, improper offset calculations cause memory corruption before the allocated buffer boundary. For detailed technical analysis, refer to the Mbed TLS Security Advisory 2024-10-1.

Detection Methods for CVE-2024-49195

Indicators of Compromise

• Unexpected application crashes or segmentation faults in services using Mbed TLS for cryptographic operations
• Memory corruption signatures detected by runtime protection mechanisms during TLS handshake or key processing
• Anomalous behavior in embedded systems or IoT devices utilizing Mbed TLS for secure communications

Detection Strategies

• Deploy memory safety tools such as AddressSanitizer (ASan) in development and testing environments to identify buffer underrun attempts
• Monitor application logs for crashes or exceptions originating from pkwrite functions or related key serialization code paths
• Implement network intrusion detection rules to identify anomalous TLS handshake patterns that may indicate exploitation attempts

Monitoring Recommendations

• Enable comprehensive logging for TLS operations in affected applications to capture potential exploitation attempts
• Deploy runtime application self-protection (RASP) solutions capable of detecting memory corruption in cryptographic operations
• Establish baseline behavior monitoring for services using Mbed TLS to identify anomalous crashes or memory access patterns

How to Mitigate CVE-2024-49195

Immediate Actions Required

• Upgrade Mbed TLS to version 3.6.2 or later immediately for all affected systems
• Audit all applications and embedded systems to identify deployments of affected Mbed TLS versions
• Review network exposure of services using Mbed TLS and consider implementing additional network-layer protections while patching is in progress

Patch Information

Arm has released Mbed TLS version 3.6.2 which addresses this buffer underrun vulnerability. Organizations should obtain the patched version from official Mbed TLS distribution channels. For complete patch details and additional security guidance, consult the Mbed TLS Security Advisory and the Mbed TLS Security Updates page.

Workarounds

• If immediate patching is not feasible, consider disabling or restricting opaque key pair operations in affected applications where possible
• Implement network segmentation to limit exposure of vulnerable services to untrusted networks
• Deploy Web Application Firewalls (WAF) or similar protective measures to filter potentially malicious TLS traffic

# Verify Mbed TLS version and upgrade
# Check current version
grep -r "MBEDTLS_VERSION" /path/to/mbedtls/include/

# Upgrade to patched version 3.6.2 or later
git clone --branch v3.6.2 https://github.com/Mbed-TLS/mbedtls.git
cd mbedtls
make
make install