CVE-2022-40617 in strongSwan
Summary
by MITRE • 10/31/2022
strongSwan before 5.9.8 allows remote attackers to cause a denial of service in the revocation plugin by sending a crafted end-entity (and intermediate CA) certificate that contains a CRL/OCSP URL that points to a server (under the attacker's control) that doesn't properly respond but (for example) just does nothing after the initial TCP handshake, or sends an excessive amount of application data.
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Analysis
by VulDB Data Team • 05/07/2025
The vulnerability identified as CVE-2022-40617 affects strongSwan versions prior to 5.9.8 and represents a significant denial of service weakness within the certificate revocation plugin. This flaw manifests when the system processes crafted certificates containing CRL or OCSP URLs that direct to attacker-controlled servers exhibiting specific response behaviors. The vulnerability operates through the certificate validation process where strongSwan attempts to verify certificate status by contacting the specified revocation servers, creating a potential attack vector that can be exploited to disrupt normal operations.
The technical implementation of this vulnerability stems from insufficient timeout mechanisms and error handling within the revocation plugin's certificate validation routines. When strongSwan encounters a certificate with a CRL or OCSP URL, it initiates network connections to verify certificate status according to standard PKI practices. However, the vulnerable versions lack proper timeout configurations and connection handling for revocation server responses, allowing attackers to craft certificates that trigger indefinite waiting states or excessive data transfer scenarios. This flaw specifically targets the network communication patterns used during certificate validation, where the system waits for responses from external servers without adequate safeguards against malicious or misconfigured endpoints.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the availability of strongSwan-based IPsec services. Attackers can exploit this weakness by constructing certificates that cause the system to enter indefinite wait states or consume excessive resources during connection attempts, effectively creating a resource exhaustion scenario that prevents legitimate certificate validation operations. The vulnerability can be particularly dangerous in environments where strongSwan serves as a critical component for secure communications, as it can be triggered through normal certificate processing flows without requiring special privileges or authentication. This makes the attack surface broader and more difficult to detect compared to other denial of service scenarios.
The root cause of this vulnerability aligns with CWE-400, which addresses "Uncontrolled Resource Consumption" in software systems, and specifically relates to improper handling of network resources during certificate validation processes. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers "Endpoint Denial of Service" through resource exhaustion, and potentially T1595.001 for initial access through certificate manipulation. The vulnerability demonstrates how certificate validation mechanisms can be weaponized to create denial of service conditions, particularly in systems that rely heavily on external revocation services for certificate status verification. Organizations using strongSwan in production environments face significant risk of service disruption and potential compromise of secure communication channels if this vulnerability remains unpatched.
Mitigation strategies for this vulnerability require immediate patching to strongSwan version 5.9.8 or later, which includes enhanced timeout mechanisms and improved error handling for revocation server communications. System administrators should also implement network-level controls to restrict access to external revocation servers, particularly when these servers are not under direct organizational control. Additional protective measures include configuring explicit timeout values for certificate validation processes, implementing monitoring for unusual connection patterns, and establishing certificate validation policies that limit the use of external revocation services when possible. Organizations should also consider implementing certificate pinning mechanisms and regular security assessments of their PKI infrastructure to prevent similar vulnerabilities from being exploited in other components of their security architecture.