CVE-2025-6013: HashiCorp Vault Auth Bypass Vulnerability

CVE-2025-6013 Overview

CVE-2025-6013 is a multi-factor authentication (MFA) enforcement bypass in HashiCorp Vault and Vault Enterprise. The flaw resides in the ldap auth method when username_as_alias is set to true. Vault may fail to enforce MFA when a directory user has multiple Common Names (CNs) that are identical except for leading or trailing whitespace. An authenticated attacker with valid LDAP credentials can exploit the inconsistent alias handling to authenticate without satisfying the configured MFA policy. HashiCorp tracks this issue under advisory HCSEC-2025-20 and classifies it as an improper neutralization of whitespace [CWE-156].

Critical Impact

Attackers with valid LDAP credentials can bypass MFA enforcement and access Vault-managed secrets, undermining a primary identity control protecting sensitive credentials and tokens.

Affected Products

• HashiCorp Vault Community Edition prior to 1.20.2
• HashiCorp Vault Enterprise prior to 1.20.2, 1.19.8, 1.18.13, and 1.16.24
• Vault deployments using the ldap auth method with username_as_alias=true

Discovery Timeline

• 2025-08-06 - CVE-2025-6013 published to NVD
• 2025-12-15 - Last updated in NVD database

Technical Details for CVE-2025-6013

Vulnerability Analysis

The vulnerability affects how Vault's LDAP authentication backend resolves a user's identity alias when username_as_alias is enabled. With this option, Vault uses the submitted username string as the entity alias rather than the canonical LDAP attribute. When a directory contains multiple CN entries that differ only by leading or trailing spaces, Vault treats these as distinct aliases for the purpose of MFA policy lookups. The MFA engine then fails to match the bound MFA requirement against the whitespace-variant alias and permits authentication without challenging the user for a second factor.

The issue is categorized as CWE-156 (Improper Neutralization of Whitespace). Authentication still requires valid LDAP credentials, but the secondary control intended to defeat credential theft is silently skipped. The attack is network-reachable against any Vault listener exposing the affected ldap auth method.

Root Cause

The root cause is missing whitespace normalization on the LDAP-derived identifier used as the entity alias. Vault's alias comparison logic treats "alice" and " alice" as different principals, but the underlying LDAP bind succeeds for both because directory servers commonly normalize CNs. The MFA enforcement layer keys its checks off the alias, so a non-canonical alias evades policy lookup.

Attack Vector

An attacker who possesses or has compromised LDAP credentials for a user whose directory entry contains CNs with whitespace variants submits the variant form to Vault's login endpoint on the LDAP auth mount. Vault accepts the bind, assigns an alias derived from the whitespace-padded username, and skips the MFA challenge that would normally apply to the canonical identity. The session token issued grants the user's full set of Vault policies. No user interaction is required and complexity is low.

No public proof-of-concept exploit is available, and the issue is not listed in the CISA Known Exploited Vulnerabilities catalog. See the HashiCorp Security Advisory HCSEC-2025-20 for vendor technical details.

Detection Methods for CVE-2025-6013

Indicators of Compromise

• Vault audit log entries showing successful auth/ldap/login events for users with MFA policies bound, but with no corresponding MFA validation event in the same request chain.
• Authentication events where the alias.name field contains leading or trailing whitespace, or differs in case/spacing from the canonical LDAP cn value.
• Successive logins for the same human user resolving to multiple distinct Vault entity aliases.

Detection Strategies

• Parse Vault audit logs and flag login operations on auth/ldap/* mounts where mfa_validation metadata is absent but the user's identity group requires MFA.
• Compare submitted usernames against canonical directory CNs and alert on whitespace or case mismatches.
• Inventory Vault auth configurations and identify any ldap mounts with username_as_alias set to true.

Monitoring Recommendations

• Forward Vault audit device output to a centralized log platform and retain authentication events for forensic review.
• Build alerts on entity alias creation events tied to ldap mounts, particularly when an entity acquires multiple aliases in a short window.
• Monitor LDAP directory changes that introduce duplicate CNs with whitespace variants, which may indicate adversary preparation.

How to Mitigate CVE-2025-6013

Immediate Actions Required

• Upgrade Vault Community Edition to 1.20.2 or later.
• Upgrade Vault Enterprise to 1.20.2, 1.19.8, 1.18.13, or 1.16.24 depending on the release branch in production.
• Audit all ldap auth method configurations for username_as_alias=true and review associated MFA bindings.
• Review LDAP directory entries for CNs containing leading or trailing whitespace and normalize them.

Patch Information

HashiCorp resolved CVE-2025-6013 in Vault Community Edition 1.20.2 and Vault Enterprise 1.20.2, 1.19.8, 1.18.13, and 1.16.24. The fix normalizes whitespace in LDAP-derived alias values so MFA policies match consistently against canonical identities. Apply patches through the standard vault package channels or the HashiCorp release archive, then restart Vault nodes following the documented upgrade procedure for HA clusters.

Workarounds

• Set username_as_alias=false on affected ldap auth mounts so Vault uses the canonical LDAP attribute for the entity alias instead of the submitted username.
• Remove or rename LDAP directory entries that contain duplicate CNs differing only by whitespace.
• Enforce MFA at an upstream identity provider or network layer until Vault can be upgraded.

# Inspect current LDAP auth configuration for the vulnerable setting
vault read auth/ldap/config

# Disable username_as_alias as a temporary mitigation
vault write auth/ldap/config username_as_alias=false