CVE-2024-27918: Coder's OIDC authentication allows email with partially matching domain to register
Summary A vulnerability in Coder's OIDC authentication could allow an attacker to bypass the CODEROIDCEMAILDOMAIN verification and create an account with an email not in the allowlist. Deployments are only affected if the OIDC provider allows users to create accounts on the provider (such as public providers like google.com).
Details During OIDC registration, the user's email was improperly validated against the allowed CODEROIDCEMAILDOMAINs. This could allow a user with a domain that only partially matched an allowed domain to successfully login or register (e.g. user@exploitcorp.com would match the allowed domain corp.com).
An attacker could register a domain name that exploited this vulnerability and register on a Coder instance with a public OIDC provider.
Impact Coder instances with OIDC enabled and protected by the CODEROIDCEMAILDOMAIN configuration.
Coder instances using a private OIDC provider are not affected, as arbitrary users cannot register through a private OIDC provider without first having an account on the provider.
Public OIDC providers (such as google.com without permitted domains set on the OAuth2 App) are impacted.
GitHub authentication and external authentication are not impacted.
Was my deployment impacted? To check if your deployment was exploited: - View the audit log on your deployment for unexpected registered users (using the action:register filter) - Check the users list for unexpected users - Users created via this exploit will have a domain that ends with one of the allowed domains but doesn’t fully match (e.g. @exploitcorp.com instead of @corp.com)
Patched Versions This vulnerability is remedied in - v2.8.4 - v2.7.3 - v2.6.1
All versions prior to these patches are affected by the vulnerability. It is recommended that customers upgrade their deployments as soon as possible if they are utilizing OIDC authentication with the CODEROIDCEMAILDOMAIN setting.
Thanks - https://github.com/arcz - https://www.trailofbits.com
References https://github.com/coder/coder/security/advisories/GHSA-7cc2-r658-7xpf https://github.com/coder/coder/commit/4439a920e454a82565e445e4376c669e3b89591c https://nvd.nist.gov/vuln/detail/CVE-2024-27918
Other sources
Coder allows oragnizations to provision remote development environments via Terraform. Prior to versions 2.6.1, 2.7.3, and 2.8.4, a vulnerability in Coder's OIDC authentication could allow an attacker to bypass the CODEROIDCEMAILDOMAIN verification and create an account with an email not in the allowlist. Deployments are only affected if the OIDC provider allows users to create accounts on the provider. During OIDC registration, the user's email was improperly validated against the allowed CODEROIDCEMAILDOMAINs. This could allow a user with a domain that only partially matched an allowed domain to successfully login or register. An attacker could register a domain name that exploited this vulnerability and register on a Coder instance with a public OIDC provider.
Coder instances with OIDC enabled and protected by the CODEROIDCEMAILDOMAIN configuration are affected. Coder instances using a private OIDC provider are not affected, as arbitrary users cannot register through a private OIDC provider without first having an account on the provider. Public OIDC providers are impacted. GitHub authentication and external authentication are not impacted. This vulnerability is remedied in versions 2.8.4, 2.7.3, and 2.6.1 All versions prior to these patches are affected by the vulnerability.It is recommended that customers upgrade their deployments as soon as possible if they are utilizing OIDC authentication with the CODEROIDCEMAILDOMAIN setting.
— MITRE
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2024-27918?
CVE-2024-27918 has a medium severity level, allowing unauthorized account creation via OIDC authentication.
How do I fix CVE-2024-27918?
To resolve CVE-2024-27918, upgrade to Coder version 0.27.4 or later for the first line or Coder v2 version 2.6.1, 2.7.3, or 2.8.4.
What software versions are affected by CVE-2024-27918?
CVE-2024-27918 affects Coder versions up to 0.27.3 and v2 versions between 2.7.0 and 2.8.0.
Is my deployment vulnerable to CVE-2024-27918?
Your deployment is vulnerable to CVE-2024-27918 if it uses an OIDC provider that allows account creation outside the `CODER_OIDC_EMAIL_DOMAIN` allowlist.
What can happen if CVE-2024-27918 is exploited?
Exploitation of CVE-2024-27918 could allow an attacker to create accounts with unauthorized email addresses, bypassing domain restrictions.