ZITADEL: Host header injection in Login V2 enables account takeover
Summary
ZITADEL versions 4.0.0 up to 4.19.4 accept untrusted public host headers in the Login V2 UI. An unauthenticated attacker who knows a victim's login name can make genuine password-reset, invite and email-verification emails contain links to the attacker's host. When the victim opens the link, or automated mail scanning fetches it, the attacker captures the single-use code and can take over the account, including instance administrators. User interaction is required, and the default Login V2 deployment is affected.
Affected
- ZITADEL 4.0.0 through 4.19.4 (including RC versions)
- Deployments using the hosted Login V2 UI; Login V1 only deployments are not affected
Fixed in
- ZITADEL 4.19.5 and later
Workaround
- No configuration fully closes the gap on unpatched versions.
- Partial mitigation: configure a fronting proxy to strip or overwrite the x-zitadel-public-host, x-zitadel-forward-host and x-forwarded-host headers on all inbound requests.
Exploitation
- Not confirmed as exploited in the wild.
- A public PoC reference is listed in a CVE digest; it has not been verified.
- Treat the exploit as public until verified otherwise.
Our recommendation
- Upgrade ZITADEL to 4.19.5 or later, updating both the main and the zitadel-login container images.
- Set the ZITADEL_SESSION_COOKIE_SECRET setting before or during the upgrade, as Login V2 email and invite verification depends on it.
- Until the upgrade is done, strip or overwrite the affected host headers at the reverse proxy.
- Check whether any ZITADEL 4.0.x to 4.19.4 instance is reachable from the internet, and prioritise it.
- Review password resets, invites and administrator logins for unexpected activity; rotate administrator credentials if a compromise is suspected.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- GitHub Security Advisory GHSA-mchc-246r-6m76 github.com
- VulnCheck advisory: ZITADEL Login V2 host header injection www.vulncheck.com
- ZITADEL releases github.com
- VulDB entry 428638 vuldb.com
- EUVD-2026-113194 vulners.com
- RedPacket Security CVE alert www.redpacketsecurity.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, 06:46.
Original description (NVD)
ZITADEL 4.0.0 before 4.19.5 contains a host header injection vulnerability in the Login V2 UI that allows unauthenticated attackers to poison password-reset, invite, and email-verification links by supplying untrusted x-zitadel-public-host, x-zitadel-forward-host, or x-forwarded-host headers. Attackers knowing a victim's login name can point the links in genuine emails at their host, harvest the single-use codes when the links are opened, and take over accounts including instance administrators.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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