CVE-2026-102339 in Telepresence
Summary
by MITRE • 11/04/2026
Telepresence enables local development against a remote Kubernetes or OpenShift cluster. Prior to 2.31.0, the Traffic Manager Tunnel gRPC streaming endpoint parses a session ID from the first bytes of a caller-controlled message in pkg/tunnel/message.go and passes it to state.Tunnel without verifying that the caller owns the active session. An attacker who obtains a valid active session ID through log leakage, cluster-internal channels, or the unauthenticated ArriveAsClient endpoint can attach a routed tunnel to that session and gain its network routing capabilities. UUID4 session IDs make cold brute force impractical. This vulnerability is fixed in 2.31.0.
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Analysis
by VulDB Data Team • 11/04/2026
The Telepresence tool facilitates local development by enabling developers to connect their local environments directly to remote Kubernetes or OpenShift clusters, effectively allowing them to test applications as if they were running within the cluster infrastructure. A critical security flaw was identified in versions prior to 2.31.0 regarding how the Traffic Manager Tunnel handles session authentication and authorization. Specifically, the gRPC streaming endpoint responsible for managing tunnels parses a session identifier from the initial bytes of incoming messages without performing adequate verification that the requesting caller actually owns or is authorized for that specific active session. This architectural oversight means that the system trusts the presence of a valid-looking session ID as sufficient proof of identity and authorization, rather than requiring cryptographic proof of ownership or binding the request to an authenticated user context.
This design flaw creates a significant risk of unauthorized access if an attacker can obtain a valid, active session identifier through various vectors such as log leakage from misconfigured systems, interception via cluster-internal network channels where traffic is not sufficiently encrypted or segmented, or by exploiting the unauthenticated ArriveAsClient endpoint which allows external entities to initiate connections without prior authentication. Once an attacker possesses this session ID, they can attach a routed tunnel to that specific session. By doing so, the attacker gains access to the same network routing capabilities and cluster connectivity privileges as the legitimate user associated with that session. This effectively bypasses intended access controls, allowing the attacker to interact with internal services, exfiltrate data, or pivot further into the protected environment using the compromised identity's permissions.
The severity of this vulnerability is somewhat mitigated by the use of UUID4 for generating session identifiers. Because UUID4 values are randomly generated and possess high entropy, cold brute force attacks aimed at guessing a valid session ID are computationally impractical and unlikely to succeed within any meaningful timeframe. However, reliance on obscurity or difficulty of discovery does not constitute security; if an attacker gains access through the aforementioned leakage channels or unauthenticated endpoints, the lack of explicit ownership verification becomes a critical failure point. The vulnerability is classified under CWE-287 Improper Authentication because the system fails to properly verify that the entity claiming the session identity is indeed authorized to do so before granting privileges associated with that session.
To mitigate this risk and prevent unauthorized tunnel attachment, organizations must ensure they upgrade Telepresence to version 2.31.0 or later where this logic has been corrected to enforce proper ownership verification of active sessions. In environments running older versions until an upgrade is possible, it is crucial to harden the surrounding infrastructure by ensuring that logs containing session identifiers are not exposed in accessible locations and that internal cluster traffic is strictly monitored for anomalies indicative of tunnel attachment attempts. Additionally, restricting access to the ArriveAsClient endpoint through network policies or authentication gateways can reduce the attack surface available to potential adversaries seeking to acquire valid session IDs. This incident highlights the importance of implementing explicit authorization checks even when strong identifiers are used, ensuring that possession of an identifier does not equate to implicit permission for all associated actions.