CVE-2026-12624 in Vault
Summary
by MITRE • 08/10/2026
Vault’s ACL policy engine did not consistently enforce a wildcard (glob) deny rule against LIST requests made with a trailing slash on the denied path. This may allow a token holding a broader allow rule alongside a narrower wildcard deny rule to enumerate the names of entries beneath a path it was intended to be denied access to. This vulnerability (CVE-2026-12624) is fixed in Vault Community Edition 2.0.3 and Vault Enterprise 2.0.3, 1.21.8, 1.20.13, and 1.19.19.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability identified as CVE-2026-12624 represents a critical access control flaw within HashiCorp Vault's Access Control List policy engine that specifically affects how wildcard deny rules are enforced against LIST operations. This issue stems from inconsistent behavior in the ACL evaluation process where trailing slashes on path specifications create unexpected authorization outcomes. The root cause lies in the policy engine's handling of glob pattern matching for LIST requests, particularly when dealing with paths that include trailing forward slashes.
The technical flaw manifests when a Vault token possesses both an allow rule that grants broad access to a parent path and a narrower wildcard deny rule targeting specific sub-paths. Under normal circumstances, the deny rule should prevent enumeration of entries within the denied scope regardless of the operation type. However, the vulnerability exploits a gap in the ACL evaluation logic where LIST requests with trailing slashes on denied paths bypass the intended restrictions, allowing unauthorized discovery of directory contents that should remain hidden.
This inconsistency creates a significant operational impact for organizations relying on Vault's access control mechanisms to protect sensitive data and infrastructure components. Attackers could leverage this weakness to perform reconnaissance activities by enumerating entries within restricted namespaces, potentially discovering sensitive service endpoints, configuration details, or other system components that should be protected from unauthorized access. The vulnerability essentially undermines the principle of least privilege by enabling information disclosure through indirect means.
The security implications extend beyond simple enumeration attacks as they can facilitate more sophisticated exploitation patterns where attackers combine this information gathering capability with other vulnerabilities to map out the entire Vault namespace structure. This behavior aligns with attack techniques documented in the MITRE ATT&CK framework under the reconnaissance phase, specifically targeting credential access and privilege escalation tactics that leverage access control bypasses.
Organizations should immediately implement mitigations including upgrading to the fixed versions of Vault Community Edition 2.0.3 and Vault Enterprise versions 2.0.3, 1.21.8, 1.20.13, and 1.19.19. Additionally, security teams should review existing ACL policies to identify and correct any instances where wildcard deny rules might be vulnerable to this specific traversal pattern. The fix addresses the underlying policy evaluation logic to ensure consistent enforcement regardless of trailing slash presence in LIST request paths.
This vulnerability classification maps to CWE-284 (Improper Access Control) and represents a failure in the principle of least privilege implementation within Vault's authorization framework. The inconsistency in ACL enforcement demonstrates the complexity of implementing robust access control mechanisms in distributed systems where path resolution patterns can create unexpected security boundaries. Organizations should conduct comprehensive audits of their Vault configurations to ensure all policy definitions properly account for this edge case in path handling behavior.
The remediation process requires careful consideration of existing policies that might be affected by the stricter enforcement, as legitimate use cases involving trailing slashes could potentially be impacted. Security teams should implement thorough testing procedures to validate that access control continues to function correctly while preventing the enumeration exploit described in CVE-2026-12624. This vulnerability serves as a reminder of the importance of rigorous testing for edge cases in security implementations and the potential consequences of inconsistent behavior in access control systems.