Teams should avoid custom scheme deep links for OAuth redirects and use App Links with verified HTTPS ownership instead. Custom schemes can be claimed by another installed app, which can intercept the authorization code and potentially exchange it for tokens if other secrets are available. App Links reduce that risk by binding the redirect target to a specific package and signing certificate.
Why OAuth redirect URIs on Android need package-bound ownership
On Android, the redirect URI is not just a routing detail, it is part of the trust boundary for the authorization code flow. If the redirect target can be claimed by another app, that app can receive the code first and potentially continue the flow before the intended app does. The security question is whether the redirect is bound to a verified app identity, not just whether it opens a screen.
Custom scheme deep links are the weak option because Android does not give them the same ownership guarantees as verified HTTPS App Links. Verified links reduce interception risk by tying the redirect to a domain the app controls, and by forcing Android to verify the package association through digital asset verification.
What changes when the redirect URI carries an authorization code
An authorization code is short-lived, but it is still valuable because it can be exchanged for tokens if the attacker also has what the flow requires next, such as a client secret, a private key, or another valid client authentication method. That means the redirect URI has to be treated as an access control decision point, not as a convenience setting.
RFC 6749: The OAuth 2.0 Authorization Framework defines the authorization code grant and the redirect-based handoff, while RFC 9700: Best Current Practice for OAuth 2.0 Security reinforces the need to reduce code interception and token theft paths. In mobile apps, that usually means preferring verified HTTPS redirects over custom schemes and avoiding designs that let a third party receive the code even briefly.
For teams that also want a broader refresher on OAuth roles, scopes, PKCE and client types, OAuth 2.0 and OpenID Connect Guide for Identity Teams is the most direct internal reference. It helps place the redirect URI decision inside the full authorization flow rather than treating it as a standalone mobile pattern.
How Android teams should implement a safer redirect pattern
Use App Links with HTTPS URLs that are verified for the app package, and keep the redirect path as narrow and explicit as possible. The goal is to make the app registration, the domain ownership, and the redirect endpoint line up so the operating system can reject other apps from handling the same callback.
Do not rely on the redirect URI alone as the only defense. PKCE remains important because it limits the value of a stolen code, and sender-constrained token designs further reduce the impact if a code or token is exposed. In other words, verified App Links are the right redirect control, but they should sit inside a flow that still assumes interception may be attempted.
SaaS-to-SaaS and OAuth App Governance Guide is useful when the mobile redirect is part of a wider OAuth integration estate, because the same class of mistakes often appears in consent, token handling and app governance. For deeper protocol context, RFC 8707: Resource Indicators for OAuth 2.0 and RFC 9449: OAuth 2.0 Demonstrating Proof of Possession show how to reduce token replay and audience confusion after the redirect is complete.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP ASVS, NIST SP 800-53 Rev 5 and CIS Controls v8 set the technical controls, while ISO/IEC 27001:2022 defines the regulatory obligations.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP ASVS | V10 — OAuth and OpenID Connect | Android redirect URIs are part of OAuth/OIDC flow security and code handling. |
| Recommendation — Require verified redirect handling and hardened OAuth client configuration. | ||
| NIST SP 800-53 Rev 5 | IA-5 — Authenticator Management | Authorization codes and related secrets must be managed to limit interception value. |
| IA-9 — Service Identification and Authentication | The app-to-authorization-server exchange depends on strong client authentication. | |
| Recommendation — Rotate and protect authenticators and related secret material used in OAuth exchanges. Use strong client authentication for token exchange after the redirect. | ||
| ISO/IEC 27001:2022 | A.8.24 — Use of cryptography | PKCE and token protection depend on correct cryptographic use in OAuth flows. |
| Recommendation — Apply cryptographic safeguards so intercepted codes cannot be reused easily. | ||
| CIS Controls v8 | CIS-6 — Access Control Management | Redirect handling must enforce least-privilege access to the auth callback path. |
| Recommendation — Restrict callback handling to the intended app and verified domain. | ||
Practitioner Guidance
What to prioritise: Treat custom scheme redirects as an exception path, not the default. If the app receives authorization codes, the first question is whether another installed app could register the same callback and see the code before your app does.
What to verify: Confirm that the redirect URI is a verified HTTPS App Link, that the Android asset links file matches the package signing certificate, and that the authorization server accepts only the exact callback pattern you intend. If any of those checks are loose, the flow is not yet safe enough to trust.
Common mistake: Teams often assume PKCE makes redirect interception harmless. It helps, but it does not fix a redirect URI that can be claimed by a different app, especially when the broader client setup still includes reusable secrets or other exchange paths.
Practitioner takeaway: For mobile OAuth, the redirect URI should be treated as part of the application’s trust boundary, and App Links are the cleaner Android control because they bind callback handling to a verified domain and package relationship.
Related resources from NHI Mgmt Group
- What breaks when redirect URIs, authorization codes, or callback handling are misconfigured in an OAuth login flow?
- How should teams handle redirect URIs across local, staging, and production environments?
- How should security teams handle fraud risk when the mobile app is the execution layer?
- How should security teams handle mobile app trust when the endpoint may be hostile?
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on September 29, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
