Summary
@better-auth/scim: account takeover and stale access via SCIM provider-id collision
Am I affected?
You are affected if your application registers the @better-auth/scim plugin and lets authenticated users generate SCIM tokens. The default canGenerateToken policy was affected, and custom policies were affected when they did not reject provider IDs already used by other account providers. The provider-ID collision issue additionally requires SSO, SAML, OIDC, generic OAuth, or social providers whose account rows use custom provider IDs, plus existing account rows under those IDs.
The deprovisioning and email-update issues require only the SCIM plugin and a valid SCIM bearer token. Published versions from @better-auth/[email protected] through 1.6.21 are affected. Beta versions from 1.7.0-beta.0 through 1.7.0-beta.9 are affected. Upgrade to @better-auth/[email protected] or 1.7.0-beta.10.
@better-auth/scim used the same logical provider ID for SCIM provider configuration and account ownership. SCIM token issuance did not reject all account-provider namespaces. An authenticated user could therefore mint a SCIM token whose provider ID matched an existing SSO, SAML, OIDC, generic OAuth, or social provider. SCIM user routes then selected account rows by that provider ID and treated those users as SCIM-managed, even when the SCIM token had never provisioned them.
The same write path had 2 additional validation issues. First, SCIM active: false was not modeled, so identity providers could receive a successful response while the user stayed active. Second, SCIM PUT and PATCH updates changed global email addresses without the same uniqueness check used by create, and emailVerified stayed unchanged after an email reassignment.
Details
The SCIM bearer middleware decoded the provider ID from the bearer token and loaded the matching scimProvider row. User listing and user lookup then queried ordinary account rows by account.providerId. This made the provider ID a user-controlled authorization key. If a SCIM token used a provider ID that belonged to SSO, SAML, OIDC, generic OAuth, or another account provider, the SCIM routes could resolve users that the token did not own.
The highest-impact path was non-organization deletion. On affected versions, DELETE /scim/v2/Users/:id for a non-organization SCIM token deleted the global Better Auth user and their sessions after resolving the user through the colliding provider ID. A low-privileged authenticated user could therefore delete users associated with a colliding provider namespace.
Organization-scoped tokens were also affected by the provider-ID collision. If the colliding provider ID matched the organization's SSO or OIDC connection, SCIM PUT or PATCH could resolve an SSO-provisioned organization member and rewrite global profile fields. Before the patch, changing a user's email through SCIM skipped the uniqueness check and left emailVerified unchanged.
SCIM deactivation had a separate failure mode. The SCIM active attribute was missing from the user schemas and PATCH mapping, so active: false was stripped from requests. A standard identity-provider deactivation signal could return success while the user kept their identity, sessions, and access.
Workarounds
If you cannot upgrade immediately, configure canGenerateToken to reject provider IDs that match any account provider ID used by your application. Include built-in providers, social providers, generic OAuth providers, SSO, SAML, and OIDC provider IDs. Also restrict which users can generate SCIM tokens.
Do not rely on deactivation reports from your identity provider until you have upgraded. Confirm that deactivated users have actually lost access, especially if your identity provider deprovisions through active: false.
If you use SCIM account linking, avoid broad domain-based linking rules. A shared email domain is not proof that a SCIM token may manage a pre-existing user. Prefer organization-membership checks or an explicit application predicate.
Audit existing scimProvider rows and remove any row whose providerId matches another account provider namespace.
Credit
Found through internal validation.
Impact
With the provider-ID collision issue, an authenticated attacker could act through a provider namespace they did not own. They could list and read SCIM user resources for users linked to the colliding provider. They could also update profile and account fields and delete global user records on the non-organization path. In organization-scoped deployments, a colliding token could mutate global profile fields for SSO-provisioned organization members.
With the deactivation issue, a terminated user could remain active after an identity provider reported successful deprovisioning through active: false. With the email-update issue, SCIM could assign one user's email to another user on adapters without an enforced unique index. That could corrupt email-keyed login and lookup, while SQL adapters could raise an unhandled adapter error.
The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.
GHSA-RJG6-39JM-RGG4 has a CVSS score of 9.9 (Critical). 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 (1.6.22, 1.7.0-beta.10); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Fixed in @better-auth/[email protected] and @better-auth/[email protected].
The patch rejects SCIM provider IDs that collide with built-in providers, configured social providers, generic OAuth providers, and SSO provider rows before a token is minted. It also scopes SCIM deletion to the SCIM account link when the user has other identities. The global user is deleted only when the SCIM account is the user's sole linked account.
The patch models the SCIM active attribute. App-level SCIM deactivation maps active: false to the admin plugin's enforced disabled-user state and revokes sessions. If the admin plugin is absent, the request is rejected instead of being silently dropped.
The patch adds the email uniqueness check to SCIM PUT and PATCH updates and resets emailVerified whenever SCIM changes a user's email.
Frequently Asked Questions
- What is GHSA-RJG6-39JM-RGG4? GHSA-RJG6-39JM-RGG4 is a critical-severity improper input validation vulnerability in @better-auth/scim (npm), affecting versions >= 1.4.0-beta.27, <= 1.6.21. It is fixed in 1.6.22, 1.7.0-beta.10. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
- How severe is GHSA-RJG6-39JM-RGG4? GHSA-RJG6-39JM-RGG4 has a CVSS score of 9.9 (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.
- Which versions of @better-auth/scim are affected by GHSA-RJG6-39JM-RGG4? @better-auth/scim (npm) versions >= 1.4.0-beta.27, <= 1.6.21 is affected.
- Is there a fix for GHSA-RJG6-39JM-RGG4? Yes. GHSA-RJG6-39JM-RGG4 is fixed in 1.6.22, 1.7.0-beta.10. Upgrade to this version or later.
- Is GHSA-RJG6-39JM-RGG4 exploitable, and should I be worried? Whether GHSA-RJG6-39JM-RGG4 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
- What actually determines whether GHSA-RJG6-39JM-RGG4 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.
- How do I fix GHSA-RJG6-39JM-RGG4?
- Upgrade
@better-auth/scimto 1.6.22 or later - Upgrade
@better-auth/scimto 1.7.0-beta.10 or later
- Upgrade