CVE-2026-39388

OpenBao's Certificate Authentication Allows Token Renewal With Different Certificate

Background

OpenBao's Certificate authentication method, when a token renewal is requested and disable_binding=true is set, attempts to verify the current request's presented mTLS certificate matches the original. Token renewals for other authentication methods do not require any supplied login information.

Workarounds

Ensure privileged roles are tightly scoped to single certificates.

Due to incorrect matching, the certificate authentication method would allow renewal of tokens for which the attacker had a sibling certificate+key signed by the same CA, but which did not necessarily match the original role or the originally supplied certificate. This implies an attacker could still authenticate to OpenBao in a similar scope, however, token renewal implies that an attacker may be able to extend the lifetime of dynamic leases held by the original token. This attack requires knowledge of either the original token or its accessor.

This vulnerability is originally from HashiCorp Vault.

The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.

CVE-2026-39388 has a CVSS score of 3.1 (Low). The vector is network-reachable, high 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 (0.0.0-20260420160924-abe84e1af4c3); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

This has been addressed in v2.5.3.

1. What is CVE-2026-39388? CVE-2026-39388 is a low-severity incorrect authorization vulnerability in github.com/openbao/openbao (go), affecting versions < 0.0.0-20260420160924-abe84e1af4c3. It is fixed in 0.0.0-20260420160924-abe84e1af4c3. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
2. How severe is CVE-2026-39388? CVE-2026-39388 has a CVSS score of 3.1 (Low). 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.
3. Which versions of github.com/openbao/openbao are affected by CVE-2026-39388? github.com/openbao/openbao (go) versions < 0.0.0-20260420160924-abe84e1af4c3 is affected.
4. Is there a fix for CVE-2026-39388? Yes. CVE-2026-39388 is fixed in 0.0.0-20260420160924-abe84e1af4c3. Upgrade to this version or later.
5. Is CVE-2026-39388 exploitable, and should I be worried? Whether CVE-2026-39388 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
6. What actually determines whether CVE-2026-39388 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.
7. How do I fix CVE-2026-39388? Upgrade github.com/openbao/openbao to 0.0.0-20260420160924-abe84e1af4c3 or later.

Other vulnerabilities in github.com/openbao/openbao