CVE-2020-15234
Redirect URL matching ignores character casing
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- High
- User interaction
- Required
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Redirect URL matching ignores character casing
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.
- Record
CVE-2020-15234- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:N - Weakness
- CWE-20, CWE-601
- Updated
- 2026-11-02
EUVDEUVD-2021-1085
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.
- Record
EUVD-2021-1085- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:N - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-grfp-q2mm-hfp6
Redirect URL matching ignores character casing
Impact
Before version v0.34.1, 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:
- Registering a client with allowed redirect URL
https://example.com/callback - Performing 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/CALLBACKwith a potentially successful OAuth2 response, depending on the state of the overall OAuth2 flow (the user might still deny the request for example).
- Record
GHSA-grfp-q2mm-hfp6- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:N - Weakness
- CWE-20, CWE-178, CWE-601
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2020-15234- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:N - CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N - CVSS 2.0
- 4.9 Medium
AV:N/AC:M/Au:S/C:P/I:P/A:N - Weakness
- CWE-20, CWE-601, CWE-178
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2020-15234- CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVGHSA-grfp-q2mm-hfp6
Redirect URL matching ignores character casing
Impact
Before version v0.34.1, 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:
- Registering a client with allowed redirect URL
https://example.com/callback - Performing 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/CALLBACKwith a potentially successful OAuth2 response, depending on the state of the overall OAuth2 flow (the user might still deny the request for example).
- Record
GHSA-grfp-q2mm-hfp6- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:N - Weakness
- CWE-178, CWE-20, CWE-601
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
github.com/ory/fositeGo |
before 0.34.1 | 0.34.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2020-15234 is a medium vulnerability (CVSS 6.1) in Ory Fosite, published October 2, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.84%, the 58th percentile. Fixed in github.com/ory/fosite 0.34.1.