# CVE-2026-44882: portainer — Fixed in 2.33.8

🐹

🐹 Go

Not in CISA KEV

HIGH severity

# CVE-2026-44882 — portainer

HIGH 

CVE-2026-44882 is a high-severity (CVSS 8.1) CWE-863 vulnerability in github.com/portainer/portainer. A fix is available for github.com/portainer/portainer — see the affected versions and patch details below.

Portainer: Kubernetes middleware continues after token validation failure, bypassing endpoint authorization

Also known as[GHSA-mgq6-4x29-88r3](/vulnerability/GHSA-mgq6-4x29-88r3)GO-2026-5505

Published

May 28, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

## Exploitation Status

### No confirmed exploitation observed yet

-   A successful exploit gives an attacker total control of the affected component, not partial access.
-   CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44882.

## EPSS Exploitation Probability

[via FIRST.org ↗](https://www.first.org/epss/)

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs27th percentile — riskier than 27% of all scored CVEsHighest risk

0.00%0.33%0.65%0.98%0.0%0.3%Jun 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/).

## How urgent is this, really

## Where this sits among everything scored

## Real-World Exposure

1 pkg affected

🐹`github.com/portainer/portainer`

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

## Description

### Summary

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.

### Severity

**High** **CWE-863** — Incorrect Authorization

Privilege required is Low — any valid Portainer session is sufficient to reach the middleware. Once the authorization outcome is bypassed, the attacker can read and modify Kubernetes resources on the target endpoint that their role should not permit — confidentiality and integrity impact are both High. No availability impact is introduced directly.

### Affected Versions

The missing `return` statement has been present since Kubernetes proxy support was introduced.

Branch

First vulnerable

Fixed in

2.33.x (LTS)

2.33.0

**2.33.8**

Portainer 2.39.0 and later are not affected — the fix was present from the initial 2.39.0 release. All releases prior to 2.33.0 are end-of-life and will not receive a fix; users on EOL versions should upgrade to a supported release.

### Workarounds

There is no configuration change that prevents the bypass directly. Administrators who cannot immediately upgrade can reduce exposure by:

-   **Restricting Kubernetes endpoint access.** Remove Portainer access to Kubernetes endpoints for users who do not require it. A user without endpoint access cannot reach `kubeClientMiddleware`.
-   **Auditing Kubernetes RBAC.** Ensure the service account Portainer uses to proxy cluster requests carries least-privilege RBAC permissions — this limits the blast radius if the bypass is exploited.

Neither of these replaces the fix.

### Affected Code

`kubeClientMiddleware` in `api/http/handler/kubernetes/handler.go` wrote the error response but did not return, allowing execution to continue with nil `tokenData`:

```
// api/http/handler/kubernetes/handler.go (pre-fix — CE and EE)
tokenData, err := security.RetrieveTokenData(r)
if err != nil {
    httperror.WriteError(w, http.StatusForbidden,
        "permission denied to access the environment", err)
    // missing return — tokenData is nil, execution continues
}

// tokenData.ID dereferenced on the next line:
_, ok := handler.KubernetesClientFactory.GetProxyKubeClient(
    strconv.Itoa(endpointID), strconv.Itoa(int(tokenData.ID)))
```

The fix adds a single return after the WriteError call in both CE and EE:

```
// post-fix
if err != nil {
    httperror.WriteError(w, http.StatusForbidden,
        "permission denied to access the environment", err)
    return
}
```

### Impact

-   Kubernetes authorization bypass. A low-privileged Portainer user can reach Kubernetes API endpoints on environments their role does not permit, with the proxy client of the legitimate session used as the vehicle.
-   Cluster resource access. Depending on the service account permissions Portainer holds on the cluster, the attacker can read or modify namespaced resources — including pods, secrets, config maps, and deployments.
-   Potential for lateral movement. Kubernetes secrets readable through this path may contain credentials for other services within the cluster or the broader infrastructure.

### Timeline

-   2026-02-16: Fix merged to develop.
-   2026-02-25: 2.39.0 released with fix.
-   2026-05-07: 2.33.8 released with backport fix.

## Affected Packages

1 total 1 fixed

Ecosystem

Package

Vulnerable range

Fix

🐹Go

`github.com/portainer/portainer` 

≥ 2.33.0&&< 2.33.8

2.33.8`go get github.com/portainer/portainer@v2.33.8`

## Affected Products

1 product · 1 configurations

Application

`portainer`portainer

≥ 2.33.0 && < 2.33.8

range

## Detection & mitigation playbook

Open-source dependency

1.  ### Detect
    
    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/portainer/portainer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
    
2.  ### Fix
    
    Update github.com/portainer/portainer to 2.33.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44882 is resolved across your whole dependency graph.
    
3.  ### Workarounds
    
    Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
    

## Frequently Asked Questions

\## Summary 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 \`kube

O3 Security · Impact-Aware SCA

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