CVE-2024-30166 in mbed TLS
Summary
by MITRE • 04/03/2024
In Mbed TLS 3.3.0 through 3.5.2 before 3.6.0, a malicious client can cause information disclosure or a denial of service because of a stack buffer over-read (of less than 256 bytes) in a TLS 1.3 server via a TLS 3.1 ClientHello.
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Analysis
by VulDB Data Team • 06/27/2025
The vulnerability identified as CVE-2024-30166 represents a critical security flaw in Mbed TLS versions ranging from 3.3.0 through 3.5.2 before the 3.6.0 release. This issue manifests as a stack buffer over-read condition that occurs within the TLS 1.3 server implementation when processing TLS 3.1 ClientHello messages. The flaw stems from inadequate input validation and memory management within the cryptographic library's handling of client handshake messages, creating a potential attack vector that could be exploited by malicious actors.
The technical implementation of this vulnerability involves a specific memory access pattern where the TLS 1.3 server processes client hello messages with malformed TLS 3.1 headers. When a malicious client sends a specially crafted ClientHello message containing TLS 3.1 protocol identifiers, the server's parsing logic fails to properly validate the message boundaries before accessing memory buffers. This results in a stack buffer over-read of less than 256 bytes, where the program attempts to read beyond the allocated memory boundaries. The vulnerability is classified under CWE-125 as an out-of-bounds read, which represents a fundamental memory safety issue in the cryptographic library's protocol handling mechanisms.
From an operational perspective, this vulnerability presents significant risks to systems relying on Mbed TLS for secure communications. The information disclosure aspect could potentially expose sensitive cryptographic material or internal memory contents to an attacker, while the denial of service component could render the affected TLS server unavailable to legitimate clients. Attackers could exploit this weakness by simply sending malformed ClientHello messages to target servers, causing unexpected behavior that may range from data leaks to complete service disruption. The attack requires minimal resources and can be executed remotely without authentication, making it particularly dangerous in production environments.
The security implications extend beyond immediate exploitation as this vulnerability affects the core TLS implementation that many applications and systems depend upon for secure communication. Organizations using affected Mbed TLS versions face potential exposure to man-in-the-middle attacks where attackers could gather sensitive information from memory dumps or cause service interruptions that impact availability. The vulnerability's impact is amplified by the widespread adoption of Mbed TLS in embedded systems, IoT devices, and enterprise applications where secure communication is critical. According to ATT&CK framework category T1592, this represents a technique for reconnaissance and initial access through protocol manipulation.
Mitigation strategies should prioritize immediate patching of affected Mbed TLS installations to version 3.6.0 or later, which contains the necessary fixes for the buffer over-read condition. System administrators should also implement network monitoring to detect suspicious ClientHello messages and consider implementing rate limiting or connection filtering mechanisms to prevent abuse of this vulnerability. Additionally, organizations should conduct thorough security assessments of their TLS implementations to identify other potential vulnerabilities in their cryptographic infrastructure. The fix addresses the root cause by implementing proper bounds checking and input validation in the TLS 1.3 server's ClientHello message parsing logic, ensuring that memory access operations remain within allocated buffer boundaries and preventing unauthorized memory reads that could compromise system security.