CVE-2026-1529 Overview
A critical security flaw was discovered in Keycloak, the popular open-source identity and access management solution. This vulnerability allows attackers to exploit improper verification of cryptographic signatures in invitation tokens, enabling unauthorized organization registration. By modifying the organization ID and target email within a legitimate invitation token's JSON Web Token (JWT) payload, attackers can bypass intended access controls and self-register into unauthorized organizations.
Critical Impact
Attackers can gain unauthorized access to protected organizations by manipulating JWT invitation tokens, potentially compromising sensitive organizational data and resources.
Affected Products
- Red Hat Keycloak (versions specified in RHSA-2026:2363)
- Red Hat Single Sign-On (versions specified in RHSA-2026:2364)
- Red Hat build of Keycloak (versions specified in RHSA-2026:2365, RHSA-2026:2366)
Discovery Timeline
- 2026-02-09 - CVE-2026-1529 published to NVD
- 2026-02-10 - Last updated in NVD database
Technical Details for CVE-2026-1529
Vulnerability Analysis
This vulnerability stems from improper verification of cryptographic signatures (CWE-347) within Keycloak's invitation token handling mechanism. When organizations invite users via email, Keycloak generates a JWT containing the organization ID and the invitee's email address. The critical flaw lies in the application's failure to properly validate the cryptographic signature of these tokens before processing the contained claims.
An attacker who obtains a valid invitation token can decode the JWT payload, modify the organization ID to target a different organization, change the email address to their own, and submit the modified token. Because the signature verification is either missing or improperly implemented, Keycloak accepts the tampered token and allows the attacker to complete registration in an organization they were never invited to join.
Root Cause
The root cause of this vulnerability is improper verification of cryptographic signatures (CWE-347) in Keycloak's invitation token validation logic. JWT tokens are designed with three parts: a header, payload, and signature. The signature cryptographically binds the header and payload together, ensuring any modification invalidates the token. However, Keycloak's implementation fails to enforce this signature verification, allowing attackers to modify the payload without detection.
Attack Vector
The attack is network-based and requires low-privilege access (having received any legitimate invitation token). The attacker intercepts or receives a valid invitation token, decodes the base64-encoded JWT payload to reveal the JSON structure containing the organization ID and email fields, modifies these values to target a different organization and their own email address, re-encodes the payload, and submits the modified token to Keycloak's registration endpoint.
The vulnerability is particularly dangerous because the attacker does not need to forge a new signature—the existing (now invalid) signature is not properly checked, and the modified token is accepted by the system.
Detection Methods for CVE-2026-1529
Indicators of Compromise
- Unusual self-registration events where the registered email does not match the original invitation recipient
- Multiple registration attempts from the same IP address targeting different organizations
- JWT tokens where the payload hash does not match the cryptographic signature
- User accounts appearing in organizations without corresponding legitimate invitation records
Detection Strategies
- Implement logging and monitoring of all invitation token usage and registration events
- Compare registered user emails against original invitation records in audit logs
- Deploy anomaly detection for registration patterns across multiple organizations
- Monitor for JWT tokens with mismatched signatures at the application layer
Monitoring Recommendations
- Enable detailed authentication and registration logging in Keycloak
- Set up alerts for registration events that bypass normal invitation workflows
- Review organization membership changes for unexpected additions
- Correlate invitation token creation timestamps with registration events
How to Mitigate CVE-2026-1529
Immediate Actions Required
- Apply the latest Keycloak security patches from Red Hat immediately
- Review recent organization registrations for potentially unauthorized users
- Audit all user accounts added via invitation tokens since deployment
- Temporarily disable invitation-based registration if patches cannot be applied immediately
Patch Information
Red Hat has released security advisories addressing this vulnerability. Apply the appropriate patches based on your deployment:
- Red Hat Security Advisory RHSA-2026:2363
- Red Hat Security Advisory RHSA-2026:2364
- Red Hat Security Advisory RHSA-2026:2365
- Red Hat Security Advisory RHSA-2026:2366
For detailed vulnerability information, refer to the Red Hat CVE-2026-1529 Details page and Red Hat Bug Report #2433783.
Workarounds
- Disable organization invitation functionality until patches are applied
- Implement additional server-side validation of invitation tokens using custom code
- Restrict invitation token usage to specific IP ranges or authenticated sessions
- Enable manual approval workflows for all new organization registrations
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
