CVE-2026-106460: Backstage: Explicit negative email verification can be ignored during shared OAuth profile normalization
Impact
Several Passport-based authentication providers use shared OAuth profile normalization from @backstage/plugin-auth-node. Affected versions may pass an email to email-based sign-in resolvers even when verification metadata supplied for that same address is explicitly negative. The ID-token-only fallback likewise did not consistently respect emailverified: false.
Exploitation requires a deployment where an admitted identity-provider user can supply or change an email address without verification and Backstage uses that profile email to resolve catalog identities. In that configuration, the user may be able to assume another catalog identity and obtain its associated access and permissions.
An absent emailverified claim is not by itself considered an affected condition. Some providers rely on authoritative organizational provisioning and intentionally omit the optional claim. Operators using email-based sign-in resolution must ensure that the configured provider restricts sign-in to the intended user population and supplies an authoritative email address, either through provider verification or trusted immutable provisioning.
This advisory covers the shared Passport profile normalization path when the selected profile email itself carries verified: false, when a matching raw provider email carries emailverified: false, or when an email obtained only from an ID token carries emailverified: false. It does not apply verification metadata from a different address or from a separate ID token to an independently fetched provider-profile email.
The generic OIDC provider follows a separate profile transform and is covered by GHSA-826h-28h9-65hg. The two advisories are complementary; deployments using both affected paths should apply both package updates. VMware Cloud uses a separate custom token transformation and is not changed by this patch.
Patches
Fixed in @backstage/plugin-auth-node versions 0.6.15 and 0.7.5. Users remaining on the 0.6.x line should upgrade to at least 0.6.15; users on 0.7.x should upgrade to at least 0.7.5.
The patched packages were released with Backstage v1.49.7 and Backstage v1.54.7, respectively. The fix is also present on master in commit 507e65a.
Workarounds
- Require the identity provider to verify user-controlled email addresses before allowing sign-in. - Ensure profile emails are immutable and provisioned from a trusted organizational source. - Use a sign-in resolver that does not depend on the profile email. - Use a custom profile transform that omits an email when matching provider metadata explicitly marks it as unverified.
Other sources
Backstage is an open framework for building developer portals. From 0.3.0 until 0.6.15 and 0.7.5, the @backstage/plugin-auth-node package did not consistently honor explicit negative email verification during shared OAuth profile normalization. The affected paths include a selected profile email marked verified: false, a matching raw provider email marked emailverified: false, and an email obtained only from an ID token marked emailverified: false. Exploitation requires an admitted identity-provider user who can supply or change an unverified email and a deployment that uses the selected profile email to resolve catalog identities. The verification metadata must apply to the selected email; an absent emailverified claim alone is not affected. In an affected configuration, the user may assume another catalog identity and obtain its associated access and permissions. This issue is fixed in versions 0.6.15 and 0.7.5.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/@backstage/plugin-auth-nodeto a version that resolves this vulnerability.Fixed in 0.7.5 - Upgrade
Upgrade
npm/@backstage/plugin-auth-nodeto a version that resolves this vulnerability.Fixed in 0.6.15 - Upgrade
Upgrade
@backstage/plugin-auth-nodeto a version that resolves this vulnerability.Fixed in 0.6.15 - Upgrade
Upgrade
@backstage/plugin-auth-nodeto a version that resolves this vulnerability.Fixed in 0.7.5 - Configuration
Use a custom profile transform that omits an email when matching provider metadata explicitly marks it as unverified.
Backstage authentication profile transform email inclusion = omit when provider metadata explicitly marks the email as unverified - Configuration
Use a sign-in resolver that does not depend on the profile email.
Backstage authentication sign-in resolver email dependency = disabled - Compensating control
Ensure profile emails are immutable and provisioned from a trusted organizational source.
- Compensating control
Require the identity provider to verify user-controlled email addresses before allowing sign-in.
Event History
Frequently Asked Questions
Which deployments are realistically exposed?
Exposure requires a deployment that uses the selected OAuth profile email to resolve catalog identities. The affected user must be an admitted identity-provider user who can supply or change an email address that is explicitly marked unverified.
Does a missing email_verified claim trigger the issue?
No. An absent email_verified claim alone is not affected; the verification metadata must explicitly indicate false for the selected email.
What could an attacker gain if exploitation succeeds?
In an affected configuration, the attacker may assume another catalog identity and receive that identity's associated access and permissions.
Which versions contain the fix?
The issue is fixed in @backstage/plugin-auth-node versions 0.6.15 and 0.7.5.