CVE-2023-32690 in libspdm
Summary
by MITRE • 06/01/2023
libspdm is a sample implementation that follows the DMTF SPDM specifications. Prior to versions 2.3.3 and 3.0, following a successful CAPABILITIES response, a libspdm Requester stores the Responder's CTExponent into its context without validation. If the Requester sends a request message that requires a cryptography operation by the Responder, such as CHALLENGE, libspdm will calculate the timeout value using the Responder's unvalidated CTExponent.
A patch is available in version 2.3.3. A workaround is also available. After completion of VCA, the Requester can check the value of the Responder's CTExponent. If it greater than or equal to 64, then the Requester can stop communication with the Responder.
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Analysis
by VulDB Data Team • 06/29/2023
The vulnerability described in CVE-2023-32690 affects the libspdm library, which implements the DMTF Security Protocol Design Model (SPDM) specifications used for secure communication between devices. This flaw exists in versions prior to 2.3.3 and 3.0, representing a critical security weakness that could potentially allow attackers to manipulate cryptographic operations within the secure channel establishment process. The vulnerability specifically targets the handling of the CTExponent parameter during the CAPABILITIES exchange phase of the SPDM protocol, where the requester stores responder information without proper validation checks.
The technical flaw manifests when a libspdm requester receives a CAPABILITIES response from a responder and stores the CTExponent value from the responder's context without validation. This unvalidated parameter is subsequently used to calculate timeout values for cryptographic operations such as CHALLENGE requests. The CTExponent parameter represents a critical cryptographic value that determines the security strength of certain cryptographic operations, and its manipulation could lead to reduced cryptographic security or predictable timeout behaviors that might be exploited by attackers. This vulnerability directly relates to CWE-20, "Improper Input Validation," and represents a failure in proper cryptographic parameter validation within the security protocol implementation.
The operational impact of this vulnerability is significant as it could enable attackers to manipulate the timeout calculations used in cryptographic operations, potentially leading to timing attacks or denial of service conditions. When the requester sends requests that require cryptographic operations, the system uses the unvalidated CTExponent value to determine timeout parameters, which could allow an attacker to influence the timing behavior of cryptographic operations. This could potentially be exploited to bypass security mechanisms or to create conditions where legitimate requests time out while malicious requests succeed. The vulnerability affects the fundamental security guarantees of the SPDM protocol implementation, particularly in scenarios involving challenge-response authentication mechanisms.
The recommended mitigation approach includes updating to version 2.3.3 or later, which includes proper validation of the CTExponent parameter. Additionally, a workaround is available that involves implementing validation checks after completing the VCA (Verification and Certification Agreement) process, where the requester explicitly checks if the responder's CTExponent value is greater than or equal to 64 and terminates communication if this condition is met. This approach aligns with ATT&CK technique T1070.006, "Indicator Removal on Host: File Deletion", in the context of preventing exploitation of the vulnerability by terminating communication before potentially harmful operations can occur. The patch addresses the core issue by implementing proper cryptographic parameter validation, ensuring that the requester does not accept potentially malicious CTExponent values that could compromise the security of cryptographic operations. This vulnerability demonstrates the importance of proper input validation in cryptographic protocol implementations and highlights how seemingly minor validation gaps can lead to significant security implications in security-critical systems.