CVE-2022-39222

Steps to reproduce

1. A victim navigates to a malicious website

2. The webserver initiates a connection with a Dex instance directly - https://dexexample.com/auth/https:%252F%252Faccounts.google.com?access_type=online&client_id=example&nonce=2AaJAimQU9CbeOFsNra1d7CJTWB&redirect_uri=http%3A%2F%2Flocalhost%3A40393%2Fauth%2Fcallback&response_type=code&scope=openid+email&state=2AaJAjhpUmsB25csCo5muvorMTl. In this example, the Dex instance is hosted on dexexample.com, and the connector is accounts.google.com.

3. Dex returns a 302 Redirect to the connector IDP, https://accounts.google.com/o/oauth2/v2/auth?client_id=237800849078-hri2ndt7gdafpf34kq8crd5sik9pe3so.apps.googleusercontent.com&redirect_uri=https%3A%2F%2Fdexexample.com%2Fauth%2Fcallback&response_type=code&scope=openid+email&state=g3dkmpontsr3ugocoddjx72ef. The attacker records the state parameter value g3dkmpontsr3ugocoddjx72ef which will be used as the request ID later on.

4. The malicious website redirects the victim’s browser to the connector IDP.

5. The user authenticates to the connector IDP. If they have authenticated before, they may not be presented with an authentication challenge. The user will silently be taken through the following steps:

   Authentication with the connector IDP, which redirects the browser to the Dex callback with a code - https://dexexample.com/callback?state=g3dkmpontsr3ugocoddjx72ef&code=4%2F0AX4XfWizg1PQEQNl18hmP0_YQ3iUYII2ed13n9ikKr_ZcV7uCZpZaPcIlxBzX5QwFIcs-w&scope=email+openid+https%3A%2F%[2Fwww.googleapis.com](http://2fwww.googleapis.com/)%2Fauth%2Fuserinfo.email&authuser=0&hd=[google.com](http://google.com/)&prompt=none

   Dex handles the callback, fetching the user claims from the connector IDP, persisting them and generating an OAuth code. Then Dex redirects the browser to the approval endpoint https://dexexample.com/approval?req=g3dkmpontsr3ugocoddjx72ef. Note that the req parameter is the same as the attacker's recorded state parameter.

   Dex uses the request ID to look up the OAuth code, and builds a redirect to the original callback with the code - http://localhost:40393/auth/callback?code=bz5p3oov2wlh5k3rboa4atxas&state=2AaJAjhpUmsB25csCo5muvorMTl.

In step 2., when the webserver initiates the connection to Dex and receives the redirect to the connector IDP, the webserver will persist the connector state parameter (g3dkmpontsr3ugocoddjx72ef), which is used as the request ID to later look up the OAuth code. As the user goes through the authentication flow with the connector IDP, the webserver will repeatedly request /approval?req=<state>. Once the user has successfully authenticated, if the webserver is able to call /approval before the victim’s browser calls /approval, then an attacker can fetch the Dex OAuth code which can be exchanged for an ID token using the /token endpoint.

Note that PKCE does not defend against this attack since the webserver initiates the request to Dex with a known code challenge.

Patches

Update to 2.35.0.

Workarounds

No known workarounds (without impacting behavior) for existing versions.

Disabling public clients is the only way to defend against attacks exploiting this vulnerability.

References

For more information

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Dex instances with public clients (and by extension, clients accepting tokens issued by those Dex instances) are affected by this vulnerability.

An attacker can exploit this vulnerability by making a victim navigate to a malicious website and guiding them through the OIDC flow, stealing the OAuth authorization code in the process. The authorization code then can be exchanged by the attacker for a token, gaining access to applications accepting that token.

The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.

CVE-2022-39222 has a CVSS score of 9.3 (Critical). The vector is network-reachable, no privileges required, and user interaction required. 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 (2.35.0); upgrading removes the vulnerable code path.

Kodem intelligence

The request has been made unpredictable with message authentication. This was accomplished by creating an HMAC using a randomly generated per-request secret. This secret is persisted between the initial login request and the approval request. Since the HMAC is derived using a secret key, its value cannot be known to an attacker, so they will be unable to poll /approval for the code.

1. What is CVE-2022-39222? CVE-2022-39222 is a critical-severity missing authorization vulnerability in github.com/dexidp/dex (go), affecting versions <= 2.34.0. It is fixed in 2.35.0. The application does not perform an authorization check before performing a sensitive operation.
2. How severe is CVE-2022-39222? CVE-2022-39222 has a CVSS score of 9.3 (Critical). 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/dexidp/dex are affected by CVE-2022-39222? github.com/dexidp/dex (go) versions <= 2.34.0 is affected.
4. Is there a fix for CVE-2022-39222? Yes. CVE-2022-39222 is fixed in 2.35.0. Upgrade to this version or later.
5. Is CVE-2022-39222 exploitable, and should I be worried? Whether CVE-2022-39222 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-2022-39222 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-2022-39222? Upgrade github.com/dexidp/dex to 2.35.0 or later.