CVE-2021-41803 is a vulnerability affecting HashiCorp Consul versions 1.8.1 up to 1.11.8, 1.12.4, and 1.13.1. The issue arises because these versions do not properly validate node or segment names before using them in JWT claim assertions within the auto configuration RPC mechanism. Specifically, the lack of validation allows an attacker with low privileges (PR:L) to supply crafted node or segment names that get interpolated into JWT claims without proper sanitization or verification. This can lead to a scenario where the attacker can manipulate the JWT claims, potentially escalating privileges or causing denial of service. The vulnerability is classified under CWE-862, which relates to missing authorization. The CVSS v3.1 base score is 7.1 (high severity), with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), requiring privileges (PR:L), no user interaction (UI:N), unchanged scope (S:U), low confidentiality impact (C:L), no integrity impact (I:N), and high availability impact (A:H). The main impact is on availability, likely due to the potential for denial of service or disruption of service through malformed JWT claims. The vulnerability was fixed in versions 1.11.9, 1.12.5, and 1.13.2 of Consul. No known exploits are reported in the wild as of the published date. Consul is a service mesh and service discovery tool widely used in cloud-native environments for service networking, configuration, and segmentation. The auto config RPC feature enables automatic configuration of nodes and segments, which is the attack surface here. Improper validation in this critical component can allow attackers to interfere with service authentication and authorization mechanisms, potentially disrupting service availability or causing misconfigurations that impact network security posture.

For European organizations, the impact of CVE-2021-41803 can be significant, especially for those relying on HashiCorp Consul for service discovery, service mesh, and network segmentation in their cloud or hybrid environments. Disruption of Consul's auto configuration RPC due to manipulated JWT claims can lead to denial of service conditions, impacting availability of critical services and applications. This can affect business continuity, especially in sectors with high dependency on microservices architectures such as finance, telecommunications, and manufacturing. Additionally, the vulnerability could be leveraged to bypass or weaken authorization controls within the service mesh, potentially exposing internal services to unauthorized access or lateral movement. Given the high availability impact and the network-exploitable nature of the vulnerability, attackers could remotely trigger service disruptions without user interaction. This elevates the risk for organizations with internet-facing Consul endpoints or insufficient network segmentation. The confidentiality impact is low, but the potential for service outages or degraded performance can have cascading effects on operational technology and customer-facing services. Compliance with European data protection regulations (e.g., GDPR) may also be indirectly affected if service disruptions impact data processing or availability guarantees.

European organizations should prioritize upgrading HashiCorp Consul to the fixed versions 1.11.9, 1.12.5, or 1.13.2 as soon as possible to remediate this vulnerability. Beyond patching, organizations should implement strict network segmentation and firewall rules to restrict access to Consul RPC endpoints, limiting exposure to trusted internal networks only. Employing mutual TLS authentication for Consul communication can further reduce the risk of unauthorized access. Monitoring and logging of Consul RPC calls should be enhanced to detect anomalous or malformed requests indicative of exploitation attempts. Organizations should also review and harden JWT claim validation logic in their Consul configurations and consider disabling auto config RPC if not required. Conducting regular security assessments and penetration testing focused on service mesh components can help identify similar weaknesses. Finally, incident response plans should include scenarios for service mesh disruptions to ensure rapid recovery and continuity.