CVE-2026-44882
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.34%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 8.1 HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
- EPSS
- 0.34% probability · 27th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-863
- Affected
- portainer/portainer
- Source
- security-advisories@github.com
References
- https://github.com/portainer/portainer/security/advisories/GHSA-mgq6-4x29-88r3Exploit, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.