# CVE-2026-6647: WSO2 Identity Server OAuth token revocation bypass with mixed-case usernames

Source: https://junglewise.ai/threats/cve-2026-6647-in-deployments-of-wso2-identity-server-configured-with-a-case  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-28. Updated: 2026-10-28  
License: CC BY 4.0 with a link back

CVE-2026-6647 · Severity: high · CVSS 7.4 · Published 2026-10-28

WSO2 Identity Server is an identity and access management platform that handles user authentication and OAuth token lifecycle. In certain configurations combining case-insensitive user stores with case-sensitive databases, the system fails to properly revoke OAuth tokens for usernames containing mixed-case characters. An attacker with a valid token for a mixed-case username can continue using that token after it should have been revoked, bypassing access control restrictions.

Technologies: [Wso2 Identity Server](https://junglewise.ai/threats/technologies/identity-server). Vendors: [Wso2](https://junglewise.ai/threats/vendors/wso2).

## Quick answers

**Is CVE-2026-6647 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-6647 being exploited in the wild.

**How severe is CVE-2026-6647?** High severity, with a CVSS score of 7.4, published 28 October 2026.

**Which products and versions are affected?** WSO2 Identity Server.

**Is there a fix for CVE-2026-6647?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-6647 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-6647?** Check whether you run Wso2 Identity Server. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A case-sensitivity mismatch in username handling during token revocation allows OAuth tokens to persist when they should be invalidated. The vulnerability occurs in Identity Server deployments where the user store treats usernames as case-insensitive but the underlying database is case-sensitive, causing mixed-case usernames to not match during revocation operations. An attacker with a valid access or refresh token can exploit this to maintain unauthorized access until token expiry.

## Affected products

- WSO2 Identity Server

## Timeline

- 2026-10-28: disclosed

## References

- [https://security.docs.wso2.com/en/latest/security-announcements/security-advisories/2026/WSO2-2026-5387/](https://security.docs.wso2.com/en/latest/security-announcements/security-advisories/2026/WSO2-2026-5387/)

## Related threats

- [WSO2 Identity Server privilege escalation via client credentials grant type](https://junglewise.ai/threats/cve-2025-11229-the-system-fails-to-properly-enforce-scope-authorization-when-the)
- [WSO2 Identity Server privilege escalation via shared database](https://junglewise.ai/threats/cve-2026-4052-this-issue-only-impacts-deployments-where-wso2-identity-server-is)
- [WSO2 Access token issuance without IDP status validation](https://junglewise.ai/threats/cve-2025-1397-when-utilizing-jwt-bearer-or-saml2-bearer-grant-types-the-system)
- [WSO2 products sensitive information disclosure in Event Publisher logs](https://junglewise.ai/threats/cve-2026-18800-when-an-event-publisher-output-adapter-is-configured-with)
- [WSO2 Identity Server content-type validation bypass](https://junglewise.ai/threats/cve-2025-13647-the-affected-component-fails-to-enforce-expected-validation)