CVE-2026-45737

The original fix for GHSA-3v3m-wc6v-x4x3 is incomplete. argocd app diff --server-side-diff can still expose Kubernetes Secret values embedded in the kubectl.kubernetes.io/last-applied-configuration annotation.

The prior fix masks top-level Secret data in ServerSideDiff responses, but it does not fully sanitize Secret data stored inside the last-applied-configuration annotation. If a Secret was previously created or updated using client-side apply, that annotation may contain raw data, stringData, and sensitive annotations. These values can be shown in UI/CLI diffs.

Details

The ServerSideDiff endpoint returns ResourceDiff.TargetState / LiveState based on server-side dry-run output. Kubernetes server-side dry-run can return a full predicted live Secret object that carries forward existing live annotations, including:

kubectl.kubernetes.io/last-applied-configuration
For Secrets created with client-side apply, that annotation can contain a JSON-serialized Secret manifest with sensitive values.

The masking path calls HideSecretData(target, live, ...). However, HideSecretData only rewrites the last-applied annotation on the second argument (live). In server-side diff, the first argument can be predictedLive, not a clean Git target. predictedLive can also contain kubectl.kubernetes.io/last-applied-configuration, so the first object’s embedded annotation can remain unmasked.

PoC

Create an app containing this Secret manifest:

apiVersion: v1
kind: Namespace
metadata:
  name: last-applied-secret-repro
---
apiVersion: v1
kind: Secret
metadata:
  name: secret
  namespace: last-applied-secret-repro
  annotations:
    app: test
    token: SECRETVAL
type: Opaque
data:
  password: U0VDUkVUVkFM
  username: U0VDUkVUVkFM

Create and Sync Argo App

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: last-applied-secret-repro
  namespace: argocd
  annotations:
    argocd.argoproj.io/compare-options: ServerSideDiff=true,IncludeMutationWebhook=true
spec:
  project: default
  destination:
    server: https://kubernetes.default.svc
    namespace: last-applied-secret-repro
  source:
    repoURL: https://github.com/YOUR_ORG/YOUR_REPO.git
    targetRevision: HEAD
    path: last-applied-secret-repro
  syncPolicy:
    automated:
      prune: true
      selfHeal: true
    syncOptions:
      - CreateNamespace=true
      - ServerSideApply=true

Run argo cd app diff
argocd app diff last-applied-secret-repro --server-side-diff --exit-code=false

❯ argocd app diff last-applied-secret-repro --server-side-diff --exit-code=false

===== /Secret last-applied-secret-repro/secret ======
10c10,11
<     kubectl.kubernetes.io/last-applied-configuration: '{"apiVersion":"v1","data":{"password":"++++++++","username":"++++++++"},"kind":"Secret","metadata":{"annotations":{"app":"test","argocd.argoproj.io/tracking-id":"last-applied-secret-repro:/Secret:last-applied-secret-repro/secret","token":"SECRETVAL"},"name":"secret","namespace":"last-applied-secret-repro"},"type":"Opaque"}'
---
>     kubectl.kubernetes.io/last-applied-configuration: |
>       {"apiVersion":"v1","data":{"password":"U0VDUkVUVkFM","username":"U0VDUkVUVkFM"},"kind":"Secret","metadata":{"annotations":{"app":"test","argocd.argoproj.io/tracking-id":"last-applied-secret-repro:/Secret:last-applied-secret-repro/secret","token":"SECRETVAL"},"name":"secret","namespace":"last-applied-secret-repro"},"type":"Opaque"}

The secret value can be seen inside the diff

Authenticated Argo CD users who can view application diffs may be able to read Secret values that should be masked.

Impacted values include:
Secret data embedded in kubectl.kubernetes.io/last-applied-configuration

CVE-2026-45737 has a CVSS score of 6.3 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.2.12, 3.3.10, 3.4.2); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-45737? CVE-2026-45737 is a medium-severity security vulnerability in github.com/argoproj/argo-cd/v3 (go), affecting versions >= 3.2.0, <= 3.2.11. It is fixed in 3.2.12, 3.3.10, 3.4.2.
2. How severe is CVE-2026-45737? CVE-2026-45737 has a CVSS score of 6.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/argoproj/argo-cd/v3 are affected by CVE-2026-45737? github.com/argoproj/argo-cd/v3 (go) versions >= 3.2.0, <= 3.2.11 is affected.
4. Is there a fix for CVE-2026-45737? Yes. CVE-2026-45737 is fixed in 3.2.12, 3.3.10, 3.4.2. Upgrade to this version or later.
5. Is CVE-2026-45737 exploitable, and should I be worried? Whether CVE-2026-45737 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-45737 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-45737?
   • Upgrade github.com/argoproj/argo-cd/v3 to 3.2.12 or later
   • Upgrade github.com/argoproj/argo-cd/v3 to 3.3.10 or later
   • Upgrade github.com/argoproj/argo-cd/v3 to 3.4.2 or later