CVE-2026-71543 in OpenBao
Summary
by MITRE • 09/21/2026
OpenBao is an open source identity-based secrets management system. Prior to 2.6.0, templated ACL, PKI, and SSH policies could substitute attacker-controlled identity data without rejecting syntax-significant characters. In ACL templated policies, asterisks, plus signs, and slashes could alter path matching. In PKI allowed_uri_sans_template and allowed_domains policies, an asterisk could broaden certificate issuance to unauthorized domains. In SSH allowed_users and allowed_domains policies, a comma could add unauthorized principals. Exploitation requires a deployment to use templated policy data that users can freely modify; templates based on the randomly generated identity.entity.id value are not affected. This could allow privilege escalation, unauthorized access, and unauthorized certificate issuance. This issue is fixed in version 2.6.0.
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Analysis
by VulDB Data Team • 09/21/2026
OpenBao serves as an open source identity-based secrets management system designed to secure application infrastructure by managing sensitive data such as passwords, API keys, and certificates. A critical vulnerability was identified in versions prior to 2.6.0 regarding the handling of templated Access Control List (ACL), Public Key Infrastructure (PKI), and Secure Shell (SSH) policies. The core technical flaw lies in the system's failure to properly sanitize or reject syntax-significant characters when substituting attacker-controlled identity data into these policy templates. This lack of input validation allows malicious actors to inject special characters that alter the logical structure of security policies, effectively bypassing intended access restrictions and expanding privileges beyond what was originally authorized by administrators.
In the context of ACL templated policies, the vulnerability permits the injection of asterisks, plus signs, and slashes into path matching rules. These characters are significant in policy syntax; for instance, an asterisk can act as a wildcard to match multiple paths, while slashes define hierarchical boundaries within the secret store. By injecting these characters through modifiable identity data, an attacker can broaden the scope of allowed operations, potentially accessing or modifying secrets that should remain restricted. This behavior aligns with CWE-77, which covers injection flaws where untrusted input is used to alter command or query structures, and maps to MITRE ATT&CK techniques related to privilege escalation via policy manipulation.
The vulnerability extends significantly into PKI certificate issuance policies through the allowed_uri_sans_template and allowed_domains configurations. When an asterisk is injected into these templates, it can broaden the scope of valid Subject Alternative Names (SANs) or domain names for which certificates are issued. This allows an attacker to obtain signed certificates for unauthorized domains that were not explicitly permitted by the organization's security policies. Such a breach undermines the trust model of public key infrastructure, enabling man-in-the-middle attacks or impersonation of legitimate services. This specific flaw relates to CWE-20, improper input validation, and impacts the integrity and authenticity guarantees provided by PKI systems.
Similarly, in SSH access control, the allowed_users and allowed_domains policies are susceptible to manipulation via comma injection. In these contexts, commas serve as delimiters separating multiple authorized principals or domains. An attacker who can influence the identity data used in templates can insert a comma followed by an unauthorized principal name, thereby adding themselves to the list of permitted users for SSH access without explicit administrative approval. This leads directly to unauthorized remote shell access and potential lateral movement within the network infrastructure. These scenarios exemplify CWE-78, improper neutralization of special elements used in an OS command, adapted here for policy configuration injection, and are categorized under MITRE ATT&CK tactics involving initial access and persistence through compromised credentials or certificates.
The operational impact of this vulnerability is severe, encompassing privilege escalation, unauthorized access to sensitive secrets, and the issuance of fraudulent digital certificates. Exploitation requires that the OpenBao deployment utilizes templated policy data derived from user-modifiable identity fields rather than immutable identifiers like the randomly generated entity ID. When templates rely on static or cryptographically random values, this attack vector is mitigated because attackers cannot control the input used for substitution. However, in environments where dynamic policies are tied to mutable attributes such as usernames or email addresses, the risk is acute. Attackers can exploit these fields to rewrite security boundaries, leading to a complete compromise of the secrets management infrastructure's integrity and confidentiality guarantees.
To mitigate this vulnerability, organizations must upgrade OpenBao to version 2.6.0 or later, where the issue has been resolved by implementing stricter validation for syntax-significant characters in templated policies. In addition to upgrading, administrators should review existing policy templates to ensure they do not rely on user-controlled identity attributes that could be manipulated via special characters. Where dynamic policies are necessary, it is advisable to use immutable identifiers such as entity IDs or UUIDs rather than mutable strings like usernames for template substitution. Regular auditing of ACL and PKI configurations against industry standards can further reduce the risk of similar injection-based attacks in future deployments.