CVE-2023-4727: Dogtag PKI Auth Bypass Vulnerability

CVE-2023-4727 Overview

A critical authentication bypass vulnerability has been discovered in dogtag-pki and pki-core, the certificate authority and identity management system used widely in Red Hat Enterprise Linux environments. The vulnerability allows attackers to bypass the token authentication scheme through LDAP injection, potentially leading to privilege escalation and unauthorized access to the PKI system.

By crafting a malicious query string parameter sessionID=*, an attacker can authenticate using any existing session stored in the LDAP directory server. This fundamentally undermines the session management security model, allowing unauthorized users to hijack legitimate sessions and gain elevated privileges within the PKI infrastructure.

Critical Impact

Attackers on adjacent networks can bypass authentication entirely and escalate privileges by hijacking existing LDAP sessions, compromising certificate authority operations and trust chains.

Affected Products

• Dogtag PKI (unpatched versions)
• pki-core (unpatched versions)
• Red Hat Enterprise Linux Certificate System (various versions - see Red Hat advisories)

Discovery Timeline

• June 11, 2024 - CVE CVE-2023-4727 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-4727

Vulnerability Analysis

This vulnerability falls under CWE-305 (Authentication Bypass by Primary Weakness), specifically manifesting as an LDAP injection flaw in the token authentication mechanism. The PKI system relies on LDAP-based session storage and retrieval for authenticating users via session tokens. However, insufficient input validation on the sessionID parameter allows attackers to inject LDAP filter wildcards.

When a user submits a session authentication request, the application constructs an LDAP query to validate the session token against stored sessions in the directory server. The vulnerable code does not properly sanitize or escape the sessionID input before incorporating it into the LDAP filter. This allows an attacker to supply a wildcard character (*) as the session identifier, which matches any existing session in the LDAP directory.

The attack requires adjacent network access, meaning the attacker must be on the same network segment as the PKI server. While this limits exposure compared to internet-facing vulnerabilities, enterprise PKI systems are often deployed on internal networks where lateral movement by attackers is a significant concern.

Root Cause

The root cause is improper input validation and sanitization of the sessionID parameter before its use in LDAP queries. The authentication system fails to implement proper LDAP escaping for special characters, allowing the wildcard operator to be interpreted as a valid LDAP filter component rather than a literal string value.

This represents a classic injection vulnerability where user-controlled input is directly incorporated into a structured query language without adequate sanitization. The LDAP protocol interprets certain characters as filter operators, and the * character specifically acts as a wildcard matching any value.

Attack Vector

The attack leverages the adjacent network attack vector, requiring the attacker to have network access to the PKI system. The exploitation flow works as follows:

1. The attacker identifies a dogtag-pki or pki-core instance accessible from their network position
2. The attacker sends an authentication request with the parameter sessionID=* to the token authentication endpoint
3. The vulnerable system constructs an LDAP filter containing the wildcard, effectively matching any stored session
4. The LDAP server returns the first matching session record
5. The authentication system accepts this as a valid session, granting the attacker access with the privileges of the hijacked session

The attack does not require any prior authentication or user interaction, and the complexity is high due to the timing requirements of having an active session available for hijacking. Successful exploitation results in complete compromise of confidentiality, integrity, and availability of the affected PKI system.

Detection Methods for CVE-2023-4727

Indicators of Compromise

• Unusual authentication requests containing wildcard characters (*) or other LDAP special characters in session parameters
• Multiple successful authentications from different source IPs using the same session token
• Anomalous LDAP query patterns in directory server logs showing filter wildcards
• Unexpected session sharing or concurrent access patterns in PKI audit logs

Detection Strategies

• Monitor authentication logs for requests containing sessionID=* or similar LDAP injection patterns
• Implement anomaly detection on LDAP query patterns to identify filter manipulation attempts
• Deploy network intrusion detection signatures targeting LDAP injection in HTTP parameters
• Enable verbose logging on PKI authentication endpoints to capture full request parameters

Monitoring Recommendations

• Enable audit logging on both the PKI server and the backend LDAP directory server
• Configure SIEM rules to alert on session parameter anomalies and LDAP special character usage
• Monitor for multiple authentication events using session identifiers that don't correlate with legitimate session creation
• Review LDAP server logs for unusual filter patterns or excessive session lookups

How to Mitigate CVE-2023-4727

Immediate Actions Required

• Apply the latest security updates from Red Hat as referenced in the security advisories RHSA-2024:4051 through RHSA-2024:4413
• Audit current PKI deployment for signs of compromise using the detection methods outlined above
• Restrict network access to PKI systems to only essential management hosts
• Enable enhanced authentication logging to support incident investigation if needed

Patch Information

Red Hat has released multiple security advisories addressing this vulnerability across different product versions. Organizations should apply the appropriate patches based on their deployed Red Hat Enterprise Linux and Certificate System versions:

• RHSA-2024:4051
• RHSA-2024:4070
• RHSA-2024:4164
• RHSA-2024:4165
• RHSA-2024:4179
• RHSA-2024:4222
• RHSA-2024:4367
• RHSA-2024:4403
• RHSA-2024:4413

For detailed technical information, consult the Red Hat CVE Analysis for CVE-2023-4727 and Red Hat Bug Report #2232218.

Workarounds

• Implement network segmentation to isolate PKI infrastructure from general network access
• Deploy a web application firewall (WAF) configured to block requests containing LDAP injection patterns
• Enable strict input validation at the network perimeter for requests to PKI authentication endpoints
• Consider implementing additional authentication factors that don't rely solely on session tokens

# Example: Restrict network access to PKI server using firewall rules
# Only allow connections from authorized management hosts
firewall-cmd --permanent --zone=internal --add-rich-rule='rule family="ipv4" source address="10.0.0.0/24" port protocol="tcp" port="8443" accept'
firewall-cmd --permanent --zone=public --add-rich-rule='rule family="ipv4" port protocol="tcp" port="8443" drop'
firewall-cmd --reload