Bug 2459948 (CVE-2026-39388)

Summary: CVE-2026-39388 OpenBao: OpenBao: Token renewal vulnerability via incorrect certificate matching in Certificate authentication.
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in OpenBao, an open source identity-based secrets management system. When renewing tokens using the Certificate authentication method with `disable_binding=true`, the system incorrectly verifies the presented mTLS (mutual Transport Layer Security) certificate. This vulnerability allows an attacker, who possesses a certificate and key signed by the same Certificate Authority (CA) as the original, to renew tokens. Such an action could extend the lifetime of dynamic leases associated with the original token, provided the attacker has knowledge of the original token or its accessor.
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Bug Depends On: 2460056, 2460057    
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Description OSIDB Bzimport 2026-04-21 02:01:46 UTC 
OpenBao is an open source identity-based secrets management system. Prior to version 2.5.3, 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. 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 original from HashiCorp Vault. This is addressed in v2.5.3. As a workaround, ensure privileged roles are tightly scoped to single certificates.