CVE-2026-44882: Portainer: Kubernetes middleware continues after token validation failure, bypassing endpoint authorization

Vulnerability summary

CVE-2026-44882 is a high (CVSS 8.1) Incorrect Authorization vulnerability in portainer. EPSS estimates a 0.34% chance of exploitation in the next 30 days, higher than 26.9% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 28-05-2026
   PublishedVulnerability first disclosed.
2. 30-05-2026
   Last modifiedVulnerability information updated.

Description

Portainer Community Edition is a lightweight service delivery platform for containerized applications that can be used to manage Docker, Swarm, Kubernetes and ACI environments. From 2.33.0 to before 2.33., Portainer proxies requests to Kubernetes clusters through a middleware layer (kubeClientMiddleware) that validates the requesting user's token before forwarding traffic to the cluster. When security.RetrieveTokenData returned an error, the middleware wrote an HTTP 403 response but was missing a return statement — execution continued into the handler with a nil tokenData value. The Kubernetes endpoints sit behind Portainer's outer AuthenticatedAccess bouncer, so an attacker requires a valid Portainer session. However, a user whose secondary token validation fails in kubeClientMiddleware — for example a user without permission to access a given Kubernetes endpoint — would have their request forwarded to the cluster anyway, bypassing the authorization check. The same defect was present in both the CE and EE codebases. This vulnerability is fixed in 2.33.8.

• CWE-863Incorrect AuthorizationThe product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.