Summary
A vulnerability was discovered in Zitadel's login V2 interface that allowed a possible account takeover.
Affected Versions
Systems running one of the following versions are affected:
- 4.x:
4.0.0through4.11.1(including RC versions)
Important Note: Although this /saml-post endpoint is used when Zitadel is integrated with a SAML Identity Provider (IdP), the vulnerability in this finding does not require Zitadel to be configured with a SAML IdP. Consequently, Zitadel is vulnerable in its default, out-of-the-box configuration.
Workarounds
The recommended solution is to upgrade to a patched version. If an upgrade is not possible and no SAML IdP integration is needed, a WAF or reverse proxy rule can be deployed to prevent access to the endpoint.
Questions
If there are any questions or comments about this advisory, please email them to [email protected]
Credits
ZITADEL extends thanks once again to Amit Laish from GE Vernova for finding and reporting the vulnerability.
Impact
Zitadel exposes an HTTP endpoint named /saml-post. This endpoint is used for handling requests to SAML IdPs and accepts two HTTP GET parameters: url and id. When these parameters are supplied, users’ browsers auto-submit an HTTP POST request to the provided url parameter.
The endpoint insecurely redirects users using the provided url GET parameter. As a result, by specifying a javascript: scheme, malicious JS code could be executed on Zitadel users’ browsers.
The endpoint also reflects user-supplied input in the server response, without HTML-encoding it. As a result, it is possible to inject arbitrary HTML code, which again leads to malicious JS code execution in the Zitadel users’ browsers.
An unauthenticated remote attacker can exploit these XSS vulnerabilities, and thus, execute malicious JavaScript code on behalf of Zitadel users. By doing so, such an attacker could reset the password of their victims, and take over their accounts.
It's important to note that this specific attack vector is mitigated for accounts that have Multi-Factor Authentication (MFA) or Passwordless authentication enabled.
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
CVE-2026-29191 has a CVSS score of 9.3 (Critical). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.12.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
The vulnerability has been addressed in the latest releases. The patch reworked the integration of SAML IdPs and the /saml-post endpoint no longer exists. Additionally, the page to change the password, now always requires the user's current password regardless of the state of the authenticated session.
4.x: Upgrade to >= 4.12.0
Frequently Asked Questions
- What is CVE-2026-29191? CVE-2026-29191 is a critical-severity cross-site scripting (XSS) vulnerability in github.com/zitadel/zitadel (go), affecting versions >= 4.0.0, < 4.12.0. It is fixed in 4.12.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- How severe is CVE-2026-29191? CVE-2026-29191 has a CVSS score of 9.3 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which packages are affected by CVE-2026-29191?
github.com/zitadel/zitadel(go) (versions >= 4.0.0, < 4.12.0)github.com/zitadel/zitadel/v2(go) (versions >= 4.0.0, < 4.12.0)
- Is there a fix for CVE-2026-29191? Yes. CVE-2026-29191 is fixed in 4.12.0. Upgrade to this version or later.
- Is CVE-2026-29191 exploitable, and should I be worried? Whether CVE-2026-29191 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-29191 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-29191?
- Upgrade
github.com/zitadel/zitadelto 4.12.0 or later - Upgrade
github.com/zitadel/zitadel/v2to 4.12.0 or later
- Upgrade