CVE-2023-49092 in RSA
Summary
by MITRE • 11/28/2023
RustCrypto/RSA is a portable RSA implementation in pure Rust. Due to a non-constant-time implementation, information about the private key is leaked through timing information which is observable over the network. An attacker may be able to use that information to recover the key. There is currently no fix available. As a workaround, avoid using the RSA crate in settings where attackers are able to observe timing information, e.g. local use on a non-compromised computer.
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Analysis
by VulDB Data Team • 11/29/2023
The vulnerability identified as CVE-2023-49092 affects the RustCrypto/RSA cryptographic library, which provides a portable RSA implementation written entirely in Rust. This particular implementation suffers from a critical security flaw that compromises the confidentiality of private keys through side-channel attacks. The vulnerability specifically stems from non-constant-time execution patterns in the cryptographic operations, creating timing variations that can be observed and analyzed by attackers. The flaw exists within the mathematical operations that form the foundation of RSA encryption and decryption processes, where the time taken to perform these operations varies based on the input values, particularly the private key components. This timing variation creates a leakage channel that allows adversaries to infer information about the private key structure through careful timing analysis of network traffic.
The technical implementation flaw manifests in the cryptographic algorithms' execution paths, where operations such as modular exponentiation and key operations do not maintain consistent execution times regardless of input values. This behavior directly violates the fundamental principle of constant-time cryptography that is essential for preventing timing attacks. The vulnerability is classified under CWE-320, which specifically addresses weaknesses in cryptographic key management, and more broadly aligns with CWE-310, which covers cryptographic weaknesses. Attackers can exploit this vulnerability by monitoring network timing information during RSA operations, particularly when the library is used in networked environments where timing variations can be measured and correlated with the underlying key material. The timing differences become particularly pronounced during private key operations, where the algorithm's behavior varies significantly based on the binary representation of the private key components.
The operational impact of this vulnerability is severe and far-reaching, particularly in environments where the affected RSA library is deployed in networked applications or services. Any system using RustCrypto/RSA in web applications, API services, or any networked infrastructure where timing information can be observed by potential attackers faces significant risk of private key compromise. The vulnerability is particularly dangerous in cloud environments, multi-tenant systems, or any scenario where an attacker has the ability to monitor network traffic timing characteristics. The lack of a fix at the time of reporting means that organizations cannot simply update their dependencies to resolve the issue, forcing them to either avoid using the library in vulnerable contexts or implement workarounds. This vulnerability directly maps to techniques described in the MITRE ATT&CK framework under T1583.001, which covers the development of tools and techniques for credential access and key compromise through side-channel attacks.
Organizations currently facing this vulnerability must implement immediate mitigations to protect their cryptographic operations and private key assets. The recommended workaround of avoiding networked use of the RSA crate on non-compromised local systems provides only partial protection, as it does not address scenarios where the library might be used in less controlled environments. Effective mitigation strategies include implementing additional timing randomization techniques, using alternative cryptographic libraries that have been verified for constant-time operations, or deploying the affected library in isolated environments where network timing observation is not possible. Security teams should also consider monitoring for unusual timing patterns in their cryptographic operations and implementing network segmentation to limit potential attack vectors. The vulnerability highlights the critical importance of constant-time implementation practices in cryptographic software development and underscores the need for comprehensive security testing that includes side-channel analysis. Given the nature of the flaw, organizations should also review their entire cryptographic stack to identify other potential instances of non-constant-time implementations that might present similar risks to their security posture.