CVE-2020-15234

Redirect URL matching ignores character casing

MEDIUM
4.8
CVSS Score
Published: October 2, 2020 at 08:40 PM UTC
Updated: June 17, 2026 at 02:56 AM UTC
1 product affected across 1 vendorFosite

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Severity
MEDIUM4.8
Exploit prediction
EPSS 0.8%

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 0.34.1
Affected range stops below 0.34.1, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
HIGH
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-20CWE-601CWE-178

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