CVE-2026-109373 zitadel CVE debrief

Who should care

Defenders responsible for ZITADEL deployments, particularly those using versions 3.0.0 before 4.19.2, should assess exposure and prioritize upgrading to prevent account takeover. This includes administrators, security teams, and operators managing ZITADEL systems. They should review system configurations, verify versions, and implement additional security controls to mitigate potential impacts.

Why it matters

CVE-2026-109373 is a critical authentication bypass vulnerability in ZITADEL 3.0.0 before 4.19.2 that allows unauthenticated attackers to obtain other users' session tokens by forging unsigned session cookies, potentially leading to account takeover and lateral movement within ZITADEL deployments.

• Potential account takeover for users with MFA-completed administrator sessions
• Possible lateral movement within ZITADEL deployments
• Required verification of ZITADEL version and upgrade to 4.19.2 or later
• Potential impact on compliance and regulatory requirements

Technical summary

The vulnerability allows unauthenticated attackers to obtain other users' session tokens by forging unsigned session cookies, potentially leading to account takeover. This is achieved by guessing time-ordered session IDs around a victim's sign-in and supplying them with empty tokens to receive rotated tokens. The vulnerability impacts ZITADEL deployments using versions 3.0.0 before 4.19.2. Defenders should prioritize verifying ZITADEL versions and upgrading to 4.19.2 or later to prevent account takeover. Additional defensive measures include implementing extra authentication and session management controls.

Defensive priority

Defenders should prioritize verifying ZITADEL versions and upgrading to 4.19.2 or later to prevent account takeover.

Recommended defensive actions

• Verify ZITADEL version and upgrade to 4.19.2 or later
• Implement additional authentication and session management controls
• Monitor for suspicious login activity
• Review compensating controls for exposed systems
• Check relevant monitoring, detection, and logs for exposed assets
• Track exceptions and retest remediated assets
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and source item provide details on the vulnerability, but additional information from vendor advisories and third-party sources may be necessary for comprehensive risk assessment. Defenders should verify ZITADEL versions and review system logs for suspicious activity. The vulnerability's impact on compliance and regulatory requirements should also be evaluated. Additional verification tasks may include reviewing system configurations and user session management.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.