CVE-2026-1518
Description
A flaw was found in Keycloak’s CIBA feature where insufficient validation of client-configured backchannel notification endpoints could allow blind server-side requests to internal services.
Statement
This LOW impact flaw in Red Hat Build of Keycloak allows a highly privileged attacker to perform blind Server-Side Request Forgery (SSRF). By configuring the CIBA backchannel notification endpoint to an internal URL, an attacker can induce Keycloak to send requests to arbitrary internal services. Exploitation requires administrative access or a valid Initial Access Token to configure client settings.
Mitigation
To mitigate this issue, restrict administrative access to Keycloak instances. Ensure that only trusted and authorized personnel have the necessary privileges to configure client settings, including the backchannel_client_notification_endpoint. This limits the ability of an attacker to manipulate the endpoint for SSRF attacks.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 2.7 | N/A | 2.7 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | High | N/A | High |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
Integrity
Technical Impact: Execute Unauthorized Code or Commands
Access Control
Technical Impact: Bypass Protection Mechanism
By providing URLs to unexpected hosts or ports, attackers can make it appear that the server is sending the request, possibly bypassing access controls such as firewalls that prevent the attackers from accessing the URLs directly. The server can be used as a proxy to conduct port scanning of hosts in internal networks, use other URLs such as that can access documents on the system (using file://), or use other protocols such as gopher:// or tftp://, which may provide greater control over the contents of requests.
Acknowledgements
Red Hat would like to thank Patrick Smith for reporting this issue.
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