ZITADEL: Session hijacking and IdP token theft via forgeable intent tokens

Summary

ZITADEL, an open-source identity provider, protects IdP intent tokens used for external identity provider logins with encryption that has no integrity check. An authenticated user with a valid account on the same instance can modify their own token so the backend accepts it for another user's pending external login. If the attacker also predicts the victim's intent identifier and wins a timing race, they can read the victim's external IdP tokens or hijack the victim's session. The attack is probabilistic and time-limited, and instances that do not use external identity providers are not affected.

Affected

• ZITADEL 4.0.0 through 4.17.2 (including RC versions)
• ZITADEL 3.0.0 through 3.4.15 (including RC versions)

Fixed in

• ZITADEL 4.x: fixed in 4.17.3
• ZITADEL 3.x: no fix; the 3.x line reached end-of-life on 2026-08-31 according to the vendor advisory. Upgrade to a patched 4.x release.

Workaround

• No configuration fully closes the gap on unpatched versions; upgrading is the recommended solution.
• Partial mitigation for self-hosted deployments: enforce strict rate limits and bot protection in front of the API, which lowers but does not eliminate the risk.

Exploitation

• Exploitation in the wild: Unknown. Not recorded in the CISA Known Exploited Vulnerabilities catalog according to one tracker.
• Public proof of concept: None found.
• CISA SSVC assessment: Exploitation none, not automatable, total technical impact.
• The vendor describes the attack as probabilistic and time-bounded (estimated success of about 1.25 percent within a 15-second window).

Our recommendation

• Upgrade all self-hosted ZITADEL instances to 4.17.3 or later.
• Retire 3.x deployments or migrate them to a patched 4.x release, because no 3.x fix will be provided.
• Check whether ZITADEL is exposed to the internet and used for external IdP login or as SSO for business applications.
• Apply strict rate limits and bot protection in front of the ZITADEL API until the upgrade is complete.
• Review the other ZITADEL vulnerabilities published on the same day and patch them together.
• Monitor authentication logs for unusual intent or session requests.

Public exploits iAttack code is publicly available (PoC on GitHub, Metasploit or Exploit-DB).

PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.

Research sources

• GitHub Security Advisory GHSA-jh3m-cr2x-qp88 github.com
• VulnCheck Advisory: ZITADEL before 4.17.3 Session Hijacking via Forgeable IdP Intent Tokens www.vulncheck.com
• OSV record CVE-2026-105208 osv.dev
• ZITADEL documentation: Login users zitadel.com
• ZITADEL GitHub security advisories github.com

Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 05:40.