GHSA-q9hr-j4rf-8fjc JWT audience claim is not verified

• Go github.com/argoproj/argo-cd: >= 1.8.2, < 2.3.14 → fixed in 2.3.14 • Go github.com/argoproj/argo-cd: >= 2.4.0, < 2.4.20 → fixed in 2.4.20 • Go github.com/argoproj/argo-cd: >= 2.5.0, < 2.5.8 → fixed in 2.5.8 • Go github.com/argoproj/argo-cd: >= 2.6.0-rc1, < 2.6.0-rc5 → fixed in 2.6.0-rc5

Impact All versions of Argo CD starting with v1.8.2 are vulnerable to an improper authorization bug causing the API to accept certain invalid tokens. OIDC providers include an `aud` (audience) claim in signed tokens. The value of that claim specifies the intended audience(s) of the token (i.e. the service or services which are meant to accept the token). Argo CD _does_ validate that the token was signed by Argo CD's configured OIDC provider. But Argo CD _does not_ validate the audience claim, so it will accept tokens that are not intended for Argo CD. If Argo CD's configured OIDC provider also serves other audiences (for example, a file storage service), then Argo CD will accept a token intended for one of those other audiences. Argo CD will grant the user privileges based on the token's `groups` claim, even though those groups were not intended to be used by Argo CD. This bug also increases the blast radius of a stolen token. If an attacker steals a valid token for a different audience, they can use it to access Argo CD. Patches A patch for this vulnerability has been released in the following Argo CD versions: • v2.6.0-rc5 • v2.5.8 • v2.4.20 • v2.3.14 The patch introduces a new `allowedAudiences` to the OIDC config block. By default, the client ID is the only allowed audience. Users who _want_ Argo CD to accept tokens intended for a different audience may use `allowedAudiences` to specify those audiences. ```yaml apiVersion: v1 kind: ConfigMap metadata: name: argocd-cm data: oidc.config: | name: Example allowedAudiences: • audience-1 • audience-2 • argocd-client-id # If `allowedAudiences` is non-empty, Argo CD's client ID must be explicitly added if you want to allow it. `` Even though the OIDC spec requires the audience claim, some tokens may not include it. To avoid a breaking change in a patch release, versions = 2.6.0, Argo CD will reject all tokens which do not have an audience claim. Users can opt into the old behavior by setting an option: ```yaml apiVersion: v1 kind: ConfigMap metadata: name: argocd-cm data: oidc.config: | name: Example skipAudienceCheckWhenTokenHasNoAudience: true ``` Workarounds There is no workaround besides upgrading. Credits The Argo CD team would like to express their gratitude to Vladimir Pouzanov (@farcaller) from Indeed, who discovered the issue, reported it confidentially according to our guidelines, and actively worked with the project to provide a remedy. Many thanks to Vladimir! References • How to configure OIDC in Argo CD • OIDC spec section discussing the audience claim • JWT spec section discussing the audience claim For more information • Open an issue in the Argo CD issue tracker or discussions • Join us on Slack in channel #argo-cd