CVE-2026-105820: 
HashiCorp Vault vulnerability analysis and mitigation

CVE-2026-105820 is an ACL policy cache namespace traversal vulnerability in HashiCorp Vault Enterprise. The flaw allows a token assigned specially crafted policy names containing path traversal constructs to use the capabilities of policies defined in other namespaces, including the root namespace. It affects Vault Enterprise versions from 0.0.1 up to (but not including) 2.1.2, with fixed versions released on October 7–8, 2026. Vault Community Edition is not affected as it does not support namespaces. The vulnerability carries a CVSS v3.1 base score of 5.4 (Medium) (GitHub Advisory, HashiCorp Advisory).

The root cause is classified as CWE-22 (Improper Limitation of a Pathname to a Restricted Directory — Path Traversal). Vault's ACL policy cache fails to properly sanitize or normalize policy names before resolving them, allowing path traversal sequences (e.g., ../) embedded in policy names to escape the intended namespace boundary and reference policies in other namespaces. Exploitation requires an authenticated token with a specially crafted policy name assigned to it, meaning the attacker must already have some level of access to the Vault environment. No public proof-of-concept code has been identified (GitHub Advisory, HashiCorp Advisory).

Successful exploitation allows an authenticated attacker to bypass namespace isolation in Vault Enterprise, gaining unauthorized access to capabilities defined in policies belonging to other namespaces — including the highly privileged root namespace. This results in low-to-moderate confidentiality and integrity impacts, as the attacker may read secrets or perform actions beyond their intended authorization scope. Availability is not directly impacted. The risk is most significant in multi-tenant Vault Enterprise deployments where namespace isolation is a critical security boundary (GitHub Advisory, HashiCorp Advisory).

There is no evidence of active in-the-wild exploitation or a publicly available proof-of-concept as of the time of disclosure. The NVD SSVC assessment classifies exploitation as "none" and the attack as non-automatable, reflecting the requirement for authenticated access with a specially crafted policy name. The EPSS score is approximately 0.249% (15th percentile), indicating a low near-term exploitation probability. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog (GitHub Advisory, HashiCorp Advisory).

1. Obtain authenticated access: Acquire a Vault token with at least low-level privileges in a non-root namespace of a vulnerable Vault Enterprise instance.
2. Craft a malicious policy name: Create or request assignment of a policy whose name contains path traversal sequences (e.g., ../../root/admin-policy) designed to resolve outside the current namespace boundary in the ACL policy cache.
3. Trigger policy cache resolution: Perform a Vault API operation that causes the ACL policy cache to resolve the crafted policy name, exploiting the lack of input sanitization to traverse into another namespace's policy space.
4. Access cross-namespace capabilities: With the traversal successful, the token gains the capabilities defined in the target namespace's policy (potentially including root namespace policies), enabling unauthorized secret reads, writes, or administrative actions beyond the attacker's intended scope (HashiCorp Advisory, GitHub Advisory).

• Logs: Vault audit logs showing tokens with policy names containing path traversal sequences (e.g., ../, %2e%2e%2f, or similar encoded variants); unexpected policy resolution events referencing namespaces other than the token's assigned namespace.
• Vault Audit: Audit log entries where a token in a child namespace successfully accesses secrets or performs operations normally restricted to the root namespace or other namespaces.
• Configuration: ACL policy names in Vault Enterprise that contain directory traversal characters (.., /, or URL-encoded equivalents) — these should be treated as suspicious and reviewed immediately.

HashiCorp has released patched versions of Vault Enterprise: 2.1.2, 1.21.12, 1.20.17, and 1.19.23. Organizations should upgrade to one of these versions as the primary remediation. As an interim measure, administrators should audit all ACL policy names across namespaces for any containing path traversal constructs and remove or rename suspicious policies. Vault Community Edition users are not affected and require no action (HashiCorp Advisory, GitHub Advisory).