CVE-2023-3817 : Vulnerability Insights and Analysis

This is about the CVE-2023-3817 vulnerability identified in OpenSSL.

Understanding CVE-2023-3817

This CVE addresses the excessive time spent checking DH q parameter value in OpenSSL, potentially leading to Denial of Service attacks.

What is CVE-2023-3817?

The vulnerability involves slow processing of excessively long DH keys or parameters in OpenSSL, affecting applications that utilize specific functions to check DH keys or parameters. This could result in significant delays and potential Denial of Service attacks if the keys are sourced from untrusted origins.

The Impact of CVE-2023-3817

Applications relying on functions like DH_check(), DH_check_ex(), or EVP_PKEY_param_check() to verify DH keys or parameters may face extended computation times, especially with large q parameter values. Attackers could exploit this to execute DoS attacks on vulnerable systems.

Technical Details of CVE-2023-3817

This section highlights key technical aspects of the CVE.

Vulnerability Description

The issue resides in the DH_check() function, which performs various checks on DH parameters. A correct q value should not exceed the modulus p parameter, rendering these checks unnecessary for q values larger than p. OpenSSL dhparam and pkeyparam command line applications are also vulnerable when utilizing the "-check" option.

Affected Systems and Versions

OpenSSL versions 1.0.2, 1.1.1, 3.0, and 3.1 up to specific build numbers are impacted by this vulnerability, while the SSL/TLS implementation remains unaffected. It is crucial to update to secure versions to mitigate the risk.

Exploitation Mechanism

By providing untrusted DH key or parameter inputs to functions like DH_check(), attackers can trigger long computations, hampering system performance and potentially leading to service disruptions.

Mitigation and Prevention

To address CVE-2023-3817 and enhance system security, several measures can be implemented.

Immediate Steps to Take

Update affected OpenSSL installations to versions that include patches addressing the vulnerability.
Monitor network activity for any signs of exploitation targeting DH key or parameter verification functions.

Long-Term Security Practices

Regularly review and update cryptographic libraries and tools to mitigate potential vulnerabilities.
Implement secure coding practices to validate inputs from untrusted sources and prevent potential DoS attacks.

Patching and Updates

Refer to the provided OpenSSL Advisory and respective git commit URLs to access patches for affected versions. Stay informed about security advisories and apply updates promptly to safeguard systems against known vulnerabilities.