CVE-2023-6057

Executive Summary

CVE-2023-6057 is a critical vulnerability in Bitdefender Total Security's HTTPS scanning functionality. The flaw lies in the improper trust of certificates issued using the DSA (Digital Signature Algorithm) signature algorithm. The product fails to properly validate the certificate chain, allowing an attacker to establish Man-in-the-Middle (MITM) SSL connections to arbitrary websites using a DSA-signed certificate. This effectively bypasses the security controls intended to protect users from malicious HTTPS traffic.

The vulnerability has a CVSS score of 0.0 (pending official scoring), but based on the description, it is likely critical. An attacker can intercept, decrypt, and potentially modify all HTTPS traffic from an affected system, leading to full compromise of confidentiality and integrity. No public proof-of-concept (PoC) or exploit code is available at this time, but the technical details are sufficient for a skilled attacker to develop one.

Supply Chain & Package Security

This vulnerability is not related to open-source package ecosystems (NPM, PyPI, Go, Ruby). It affects a proprietary commercial security product (Bitdefender Total Security). The supply chain risk is limited to the distribution of the Bitdefender software itself, which is typically downloaded from official vendor channels. Users should ensure they are using the latest version from the official Bitdefender website.

CVSS Breakdown & Threat Level

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

• Attack Vector (AV): Network (N) – The attacker can exploit this remotely.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – The victim does not need to perform any action.
• Scope (S): Unchanged (U) – The vulnerable component and the affected resource are the same.
• Confidentiality (C): High (H) – Full disclosure of all HTTPS traffic.
• Integrity (I): High (H) – Attacker can modify traffic in transit.
• Availability (A): High (H) – Attacker could potentially disrupt service.

Threat Level: Critical. The vulnerability allows a complete bypass of HTTPS security, enabling full MITM attacks without user interaction.

Deep Dive & Mechanics

The vulnerability resides in Bitdefender Total Security's HTTPS scanning module. This module is designed to intercept and inspect HTTPS traffic for malware and threats. To do this, it acts as a local proxy, generating certificates on-the-fly to re-encrypt traffic after inspection.

The flaw is in the certificate validation logic. When the HTTPS scanner encounters a certificate signed with the DSA algorithm, it improperly trusts it without verifying the full certificate chain. Specifically, the scanner does not check whether the DSA-signed certificate chains back to a trusted root CA. This allows an attacker to present a self-signed or otherwise invalid DSA certificate, and the scanner will accept it as valid.

Attack Scenario:

1. An attacker on the same network (e.g., public Wi-Fi) performs ARP spoofing or DNS poisoning to redirect the victim's traffic through the attacker's machine.
2. The victim's Bitdefender Total Security intercepts the HTTPS connection to a legitimate site (e.g., bank.com).
3. The attacker presents a DSA-signed certificate for bank.com. This certificate is not issued by a trusted CA, but Bitdefender's scanner trusts it due to the bug.
4. The scanner re-encrypts the traffic using this untrusted certificate, and the victim's browser sees a valid HTTPS connection (because the scanner's root CA is trusted by the system).
5. The attacker can now decrypt, read, and modify all data exchanged between the victim and bank.com.

The vulnerability is particularly dangerous because it requires no user interaction and can be exploited from the same network segment.

Vulnerable vs. Patched Code

No official patch has been released. The vulnerable code is in the certificate validation routine of the HTTPS scanning module. The following is a conceptual representation of the flawed logic:

Vulnerable Code (Pseudocode):

bool validate_certificate(X509 *cert) {
    // Check if certificate is signed with DSA
    if (cert->sig_alg == NID_dsaWithSHA1 || cert->sig_alg == NID_dsaWithSHA256) {
        // BUG: Trust DSA certificates without chain validation
        return true;
    }
    // Normal chain validation for other algorithms
    return verify_chain(cert);
}

Patched Code (Hypothetical):

bool validate_certificate(X509 *cert) {
    // Perform full chain validation regardless of signature algorithm
    if (!verify_chain(cert)) {
        return false;
    }
    // Additional check: ensure the certificate is signed by a trusted CA
    if (!is_trusted_issuer(cert)) {
        return false;
    }
    return true;
}

The fix would involve removing the special case for DSA-signed certificates and ensuring all certificates undergo the same rigorous chain validation.

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• Attacker and victim on the same network segment.
• Ability to perform ARP spoofing or DNS poisoning.
• A machine with a tool like mitmproxy or bettercap.

Lab Setup:

1. Network Setup: Use a virtual lab with two VMs (Kali Linux as attacker, Windows 10 with Bitdefender Total Security as victim) on a host-only network.
2. ARP Spoofing: On Kali, use arpspoof to redirect traffic:

   echo 1 > /proc/sys/net/ipv4/ip_forward
   arpspoof -i eth0 -t 192.168.1.10 192.168.1.1
   arpspoof -i eth0 -t 192.168.1.1 192.168.1.10
   

3. Generate DSA Certificate: Create a self-signed DSA certificate for the target domain:

   openssl dsaparam -out dsaparam.pem 2048
   openssl gendsa -out dsa_private.pem dsaparam.pem
   openssl req -new -x509 -key dsa_private.pem -out dsa_cert.pem -days 365 -subj "/CN=bank.com"
   

4. MITM Proxy: Use mitmproxy with the DSA certificate:

   mitmproxy --listen-port 8080 --cert dsa_cert.pem
   

5. Redirect Traffic: Use iptables to redirect HTTP/HTTPS traffic to the proxy:

   iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080
   iptables -t nat -A PREROUTING -p tcp --dport 443 -j REDIRECT --to-port 8080
   

6. Trigger: Victim visits https://bank.com. Bitdefender's scanner will trust the DSA certificate, and the attacker can capture credentials.

Note: No public exploit code is available. The above is a conceptual lab setup.

Blue Team (Defender)

Detection:

• Monitor for unusual certificate chains in HTTPS traffic, especially DSA-signed certificates.
• Use network monitoring tools to detect ARP spoofing (e.g., arpwatch).
• Enable logging on Bitdefender to capture certificate validation failures.

Mitigation:

• Disable HTTPS scanning in Bitdefender Total Security until a patch is available (temporary workaround).
• Use a VPN to encrypt traffic at a lower layer, making MITM harder.
• Implement network segmentation to limit attacker access.

Indicators of Compromise (IOCs)

• Network:
  • Presence of DSA-signed certificates in HTTPS traffic (unusual for modern web).
  • ARP cache inconsistencies (multiple IPs for same MAC).
  • Unexpected SSL/TLS certificate warnings in browsers (though Bitdefender may suppress them).
• Host:
  • Bitdefender logs showing certificate validation errors for DSA algorithms.
  • Unusual outbound connections from the Bitdefender process.
• File:
  • Self-signed DSA certificates on the network (e.g., dsa_cert.pem).

Detection Engineering

YARA Rule

rule CVE_2023_6057_DSA_Certificate {
    meta:
        description = "Detects DSA-signed certificates that may indicate exploitation of CVE-2023-6057"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-6057"
    strings:
        $dsa_oid = { 2a 86 48 ce 38 04 01 } // DSA with SHA1 OID
        $dsa_oid2 = { 2a 86 48 ce 38 04 03 } // DSA with SHA256 OID
    condition:
        any of ($dsa_oid*) and filesize < 10KB
}

Sigma Rule

title: CVE-2023-6057 - DSA Certificate in HTTPS Traffic
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects DSA-signed certificates in network traffic, indicating possible exploitation of CVE-2023-6057
author: Valters IT
date: 2025-04-10
logsource:
    category: network_connection
    product: zeek
detection:
    selection:
        certificate.algorithm: "dsa"
    condition: selection
falsepositives:
    - Legacy systems using DSA certificates (rare)
level: high

Suricata Rule

alert tls any any -> any any (msg:"CVE-2023-6057 - DSA Certificate Detected"; flow:to_server; tls.cert_algorithm:"dsa"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable HTTPS Scanning: Temporarily disable the HTTPS scanning feature in Bitdefender Total Security to prevent exploitation.
   • Open Bitdefender > Settings > Protection > Online Threat Prevention > Manage Exceptions > Turn off "Scan SSL".
2. Monitor for Updates: Check the Bitdefender website or support channels for a security patch.
3. Network Controls: Implement network segmentation and use VPNs for sensitive communications.

Long-Term Fix:

• Apply the official patch from Bitdefender once released.
• Ensure all systems are updated to the latest version of Bitdefender Total Security.

Workarounds:

• Use an alternative antivirus solution with proper HTTPS scanning.
• Educate users to avoid untrusted networks (e.g., public Wi-Fi) without a VPN.

Valters IT