CVE-2026-18679 in Kuma
Summary
by MITRE • 08/12/2026
When kuma-dp is started against an HTTPS control plane and the operator did not pass a CA certificate, the data plane connects with TLS peer verification disabled, and the dataplane authentication token is sent over that unverified connection.
An on-path actor can intercept the dataplane authentication token and impersonate the control plane to the data plane, injecting a forged bootstrap configuration and taking over the proxy.
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Analysis
by VulDB Data Team • 08/12/2026
This vulnerability represents a critical security flaw in the kuma data plane proxy implementation where improper TLS configuration leads to authentication token exposure. When kuma-dp initializes communication with an HTTPS control plane and no explicit CA certificate is provided by the operator, the system defaults to disabling TLS peer verification. This configuration oversight creates a man-in-the-middle attack vector that directly compromises the integrity of the control plane communication channel.
The technical implementation flaw stems from the lack of proper certificate validation mechanisms within the kuma-dp component. According to CWE-295, this represents a weakness in certificate validation where the system fails to properly verify the authenticity of the TLS peer. The vulnerability manifests when the data plane proxy establishes an encrypted connection without validating the control plane's certificate authority, leaving the communication channel susceptible to interception attacks.
The operational impact of this vulnerability is severe as it enables attackers positioned on the network path between the data plane and control plane to capture authentication tokens transmitted over the unverified TLS connection. This attack vector aligns with ATT&CK technique T1071.004 for application layer protocol traffic encryption and T1566 for credential access through interception methods. Once an attacker intercepts the authentication token, they can impersonate the control plane to the data plane, effectively gaining administrative control over the proxy configuration.
The attack scenario involves an on-path actor who can monitor network traffic between kuma-dp and the control plane. This actor captures the authentication token during the initial handshake process when TLS peer verification is disabled. The forged bootstrap configuration injection allows the attacker to manipulate how the data plane operates, potentially redirecting traffic, modifying routing rules, or executing arbitrary commands through the compromised proxy.
Mitigation strategies should focus on enforcing mandatory certificate validation for all control plane communications. Operators must explicitly provide CA certificates when configuring kuma-dp to ensure proper TLS peer verification. The implementation should enforce strict certificate validation using established trust chains rather than falling back to insecure default configurations. Additionally, organizations should implement network monitoring to detect unusual authentication token exchanges and consider deploying secure communication channels that prevent interception attacks through network segmentation or additional encryption layers.