CVE-2018-0487 in ARM mbed TLS
Summary
by MITRE
ARM mbed TLS before 1.3.22, before 2.1.10, and before 2.7.0 allows remote attackers to execute arbitrary code or cause a denial of service (buffer overflow) via a crafted certificate chain that is mishandled during RSASSA-PSS signature verification within a TLS or DTLS session.
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Analysis
by VulDB Data Team • 02/06/2023
The vulnerability identified as CVE-2018-0487 represents a critical buffer overflow flaw within the ARM mbed TLS cryptographic library that affects multiple version ranges including 1.3.21 and earlier, 2.1.9 and earlier, and 2.6.9 and earlier. This vulnerability specifically targets the RSASSA-PSS signature verification process during TLS or DTLS session establishment, creating a pathway for remote attackers to potentially execute arbitrary code or cause system-wide denial of service conditions. The flaw occurs when the library improperly handles crafted certificate chains that contain maliciously constructed signature parameters, leading to memory corruption that can be exploited by attackers positioned remotely in the network.
The technical root cause of this vulnerability stems from inadequate input validation and memory management during the cryptographic signature verification process. When mbed TLS processes a certificate chain containing a specially crafted RSASSA-PSS signature, the library fails to properly bounds-check the signature data before attempting to parse and verify it. This oversight creates a classic buffer overflow condition where attacker-controlled data can overwrite adjacent memory locations, potentially allowing for code execution or system instability. The vulnerability operates at the cryptographic protocol level, making it particularly dangerous as it can be triggered during normal TLS/DTLS handshake operations without requiring any special privileges or local access.
From an operational impact perspective, this vulnerability poses significant risks to any system relying on mbed TLS for secure communications, particularly those implementing TLS or DTLS protocols for network security. The remote exploitability means that attackers can target vulnerable systems from anywhere on the network, making it particularly dangerous for web servers, VPN gateways, IoT devices, and any network infrastructure that uses the affected library versions. The potential for arbitrary code execution provides attackers with full control over affected systems, while the denial of service component can be used to disrupt legitimate services and create availability issues. Organizations using vulnerable versions of mbed TLS may experience complete system compromise or service disruption depending on how the vulnerability is exploited.
The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a specific instance of improper input validation during cryptographic operations. From an ATT&CK framework perspective, this vulnerability maps to T1059 for remote code execution capabilities and T1499 for denial of service attacks, with potential for privilege escalation if exploited successfully. The attack surface includes any application or service that utilizes mbed TLS for secure communications, particularly web servers, network appliances, and embedded systems. Organizations should immediately assess their deployment of mbed TLS versions and implement patches to address this vulnerability, as the remote nature of the exploit means that systems may be compromised without any direct interaction from administrators.
Mitigation strategies should focus on immediate version upgrades to mbed TLS 1.3.22, 2.1.10, or 2.7.0, which contain the necessary fixes for the buffer overflow condition. Additionally, network segmentation and firewall rules can be implemented to limit exposure of vulnerable systems to untrusted networks, while monitoring systems should be deployed to detect potential exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of vulnerable software, and organizations should establish processes for rapid patch deployment across their infrastructure. The fix implemented in the patched versions addresses the specific memory handling issues during RSASSA-PSS signature verification, preventing the buffer overflow condition that enables both remote code execution and denial of service attacks.