CVE-2026-1518
📋 TL;DR
This vulnerability in Keycloak's CIBA (Client Initiated Backchannel Authentication) feature allows attackers to make blind server-side requests to internal services by exploiting insufficient validation of client-configured backchannel notification endpoints. It affects Keycloak deployments using the CIBA feature. The impact is limited to internal network scanning and potential information disclosure.
💻 Affected Systems
- Keycloak
⚠️ Risk & Real-World Impact
Worst Case
Attackers could map internal network services, potentially discovering vulnerable internal systems or sensitive information through blind SSRF responses.
Likely Case
Limited internal network reconnaissance, potentially identifying internal service banners or error messages.
If Mitigated
Minimal impact with proper network segmentation and endpoint validation controls in place.
🎯 Exploit Status
Requires ability to configure client backchannel notification endpoints and knowledge of internal network targets.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Keycloak 25.0.2 or later
Vendor Advisory: https://access.redhat.com/security/cve/CVE-2026-1518
Restart Required: Yes
Instructions:
1. Upgrade to Keycloak 25.0.2 or later. 2. Restart Keycloak service. 3. Verify CIBA client configurations validate notification endpoints properly.
🔧 Temporary Workarounds
Disable CIBA Feature
allTemporarily disable Client Initiated Backchannel Authentication if not required
Set 'ciba-enabled' to false in Keycloak configuration
Restrict Client Configuration
allLimit which clients can configure backchannel notification endpoints
Review and restrict client configuration permissions in Keycloak admin console
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Keycloak from internal services
- Deploy web application firewall rules to block suspicious backchannel notification patterns
🔍 How to Verify
Check if Vulnerable:
Check if running Keycloak version <25.0.2 with CIBA feature enabled. Review client configurations for unrestricted backchannel notification endpoints.Check Version:
keycloak/bin/kc.sh --version (Linux) or check Keycloak admin console version infoVerify Fix Applied:
After patching, test that client-configured backchannel notification endpoints are properly validated and cannot target internal network addresses.📡 Detection & Monitoring
Log Indicators:
- Unusual backchannel notification requests to internal IP addresses
- Failed CIBA authentication attempts with suspicious endpoints
Network Indicators:
- Outbound HTTP requests from Keycloak to internal network ranges on non-standard ports
- SSRF-like patterns in Keycloak server traffic
SIEM Query:
source="keycloak" AND ("backchannel" OR "ciba") AND (dst_ip=10.0.0.0/8 OR dst_ip=172.16.0.0/12 OR dst_ip=192.168.0.0/16)