RFC 9207 Breaking Change: GitHub OAuth Sign-In Failing in NextAuth, oauth2-proxy, Spring Security (April 6-10, 2026)

[Vinay152003]

🏷️ Discussion Type

Bug

💬 Feature/Topic Area

Supply chain security

Discussion Details

Problem Statement
GitHub recently implemented RFC 9207 (OAuth 2.0 Authorization Server Issuer Identification) by silently returning an iss parameter in OAuth callback responses. Between April 6-10, 2026, GitHub began sending:

iss=https://github.com/login/oauth

This change has completely broken GitHub OAuth sign-in across dozens of popular open-source projects and frameworks:

✅ NextAuth v4 (28.2k⭐) — Used by 1000s of SaaS companies

Error Message
[next-auth][error][OAUTH_CALLBACK_ERROR]
issuer must be configured on the issuer

Authentication fails completely — users cannot sign in via GitHub at all.

Root Cause
openid-client library validates the iss parameter unconditionally. GitHub provider configurations do NOT set issuer, causing validation to fail immediately.

Evidence
Langfuse self-hosted deployment (AWS ALB logs):

April 6: All callbacks successful (no iss parameter)
April 10: All callbacks contain iss, all fail
Reference Issue: Langfuse #13091

Solution
Add issuer: "https://github.com/login/oauth" to GitHub OAuth provider configuration.

GitHubProvider({
clientId: process.env.GITHUB_CLIENT_ID,
clientSecret: process.env.GITHUB_CLIENT_SECRET,
issuer: "https://github.com/login/oauth", // ← ADD THIS
})

Questions
Is this an announced change? No — no GitHub Changelog entry
Will there be a grace period? Unknown
Should frameworks fix this? Yes — NextAuth, oauth2-proxy, Spring Security need updates
Timeline
April 6, 2026: GitHub silently begins returning iss
April 10, 2026: Widespread failures reported
April 10, 2026: Langfuse files issue #13091
Related Resources
Langfuse Issue #13091 - Original bug report
RFC 9207 Specification
Tracking Repository
#github-oauth #rfc-9207 #breaking-change #nextauth #oauth2-proxy #authentication

[github-actions[bot]]

💬 Your Product Feedback Has Been Submitted 🎉

Thank you for taking the time to share your insights with us! Your feedback is invaluable as we build a better GitHub experience for all our users.

Here's what you can expect moving forward ⏩

• Your input will be carefully reviewed and cataloged by members of our product teams. 
  • Due to the high volume of submissions, we may not always be able to provide individual responses.
  • Rest assured, your feedback will help chart our course for product improvements.
• Other users may engage with your post, sharing their own perspectives or experiences. 
• GitHub staff may reach out for further clarification or insight. 
  • We may 'Answer' your discussion if there is a current solution, workaround, or roadmap/changelog post related to the feedback.

Where to look to see what's shipping 👀

• Read the Changelog for real-time updates on the latest GitHub features, enhancements, and calls for feedback.
• Explore our Product Roadmap, which details upcoming major releases and initiatives.

What you can do in the meantime 💻

• Upvote and comment on other user feedback Discussions that resonate with you.
• Add more information at any point! Useful details include: use cases, relevant labels, desired outcomes, and any accompanying screenshots.

As a member of the GitHub community, your participation is essential. While we can't promise that every suggestion will be implemented, we want to emphasize that your feedback is instrumental in guiding our decisions and priorities.

Thank you once again for your contribution to making GitHub even better! We're grateful for your ongoing support and collaboration in shaping the future of our platform. ⭐

[hpsin]

Hi @Vinay152003 - thanks for opening this and your PR in Next-auth!
We did start rolling out the iss value in the code response ahead of a planned release on Monday, under the expectation that it'd be a non-breaking change. Given the issue with next-auth we're putting that on hold while they cut new releases and folks get to update their apps to configure an issuer for GitHub.

We'll be announcing changes to the metadata documents to get them up to date and correct on Monday, hopefully, with some heads up going out ASAP just so folks get a little awareness (in case they're somehow dependent on the wrong information being in one of the metadata documents).

[Vinay152003]

Thanks @hpsin ! Glad my PR and discussion help.