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CVE-2026-44882

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

8.1 HighFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
None

Exploit likelihood

0.34%Up 0.3 points since May 29, 2026
90%50%10%1%

What each source reports

CVE List Score used 8.1

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

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.

Record
CVE-2026-44882
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-863
Updated
2026-11-02
EUVDEUVD-2026-33060 8.1

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.

Record
EUVD-2026-33060
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-mgq6-4x29-88r3 8.1

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

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:…
Record
GHSA-mgq6-4x29-88r3
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-863
Updated
2026-11-02
NVD 8.1

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.

Record
CVE-2026-44882
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-863
Updated
2026-11-02
OSV 8.1

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

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.

Record
CVE-2026-44882
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-863
Updated
2026-11-02
OSVGHSA-mgq6-4x29-88r3 8.1

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

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:…
Record
GHSA-mgq6-4x29-88r3
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-863
Updated
2026-11-02
OSVGO-2026-5505 No score

Portainer's Kubernetes middleware continues after token validation failure, bypassing endpoint authorization in github.com/portainer/portainer

Portainer's Kubernetes middleware continues after token validation failure, bypassing endpoint authorization in github.com/portainer/portainer.

NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions.

(If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.)

The additional affected modules and versions are: github.com/portainer/portainer from v2.33.0 before v2.33.8.

Record
GO-2026-5505
Updated
2026-11-02
OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
  • GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
  • GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
  • GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
  • GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
  • GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
  • GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
  • GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
  • GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
  • GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
  • GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
  • GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
  • GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
  • GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
  • GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
  • GO-2026-5933 GHSA-3g4q-2f67-2gvh
  • GO-2026-5934 GHSA-59qp-cfj3-rp64
  • GO-2026-5935 GHSA-7856-g3gv-9wq8
  • GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
  • GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
  • GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
  • GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
  • GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
  • GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
  • GO-2026-5942 CVE-2026-46600
  • GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
  • GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
  • GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
  • GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
  • GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
  • GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
  • GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
  • GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
  • GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
  • GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
  • GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
  • GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
  • GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
  • GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
  • GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
  • GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
  • GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
  • GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
  • GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
  • GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
  • GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
  • GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
  • GO-2026-5969 GHSA-g936-7jqj-mwv8
  • GO-2026-5970 CVE-2026-56852
  • GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
  • GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
  • GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
  • GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
  • GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
  • GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
  • GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
  • GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
  • GO-2026-5981 GHSA-mqxv-9rm6-w8qc
  • GO-2026-5982 GHSA-pqg7-v6wh-3pfp
  • GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
  • GO-2026-5985 GHSA-7rx3-5wx3-5v76
  • GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
  • GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
  • GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
  • GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
  • GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
  • GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
  • GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
  • GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
  • GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
  • GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
  • GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
  • GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
  • GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
  • GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
  • GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
  • GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…
Record
openSUSE-SU-2026:21483-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/portainer/portainer
Go
 2.33.0 up to 2.33.8
2.33.8
github.com/portainer/portainer
Go
 All versions None known
govulncheck-vulndb
openSUSE:Leap 16.0
From an advisory covering 1734 CVEs
 before 0.0.20260723T184607-160000.1.1
0.0.20260723T184607-160000.1.1

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-44882 is a high vulnerability (CVSS 8.1) in Portainer, published May 14, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.34%, the 27th percentile. Fixed in github.com/portainer/portainer 2.33.8.

References

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