Summary
OpenBao has Reflected XSS in its OIDC authentication error message
Workarounds
The vulnerability can be mitigated by removing any roles with callback_mode set to direct.
Impact
OpenBao installations that have an OIDC/JWT authentication method enabled and a role with callback_mode=direct configured are vulnerable to XSS via the error_description parameter on the page for a failed authentication.
This allows an attacker access to the token used in the Web UI by a victim.
The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.
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.
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The error_description parameter has been replaced with a static error message in v2.5.2
Frequently Asked Questions
- What is CVE-2026-33758? CVE-2026-33758 is a critical-severity improper input validation vulnerability in github.com/openbao/openbao (go), affecting versions < 0.0.0-20260325133417-6e2b2dd84f0e. It is fixed in 0.0.0-20260325133417-6e2b2dd84f0e. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
- Which versions of github.com/openbao/openbao are affected by CVE-2026-33758? github.com/openbao/openbao (go) versions < 0.0.0-20260325133417-6e2b2dd84f0e is affected.
- Is there a fix for CVE-2026-33758? Yes. CVE-2026-33758 is fixed in 0.0.0-20260325133417-6e2b2dd84f0e. Upgrade to this version or later.
- Is CVE-2026-33758 exploitable, and should I be worried? Whether CVE-2026-33758 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-2026-33758 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-2026-33758? Upgrade
github.com/openbao/openbaoto 0.0.0-20260325133417-6e2b2dd84f0e or later.