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Port 5061 – SIP-TLS (Secure SIP)

Service:

sip

Protocol:

TCP

Port:

5061

Used for:

Secure SIP over TLS for encrypted VoIP

Why It’s Open

Port 5061 is used for Session Initiation Protocol over TLS (SIP-TLS), offering encrypted signaling for VoIP and other real-time communications. Unlike standard SIP on port 5060, SIP over TLS ensures that call setup, registration, and signaling data are protected from eavesdropping and tampering.

Organizations implement this port in secure VoIP environments, especially in business, healthcare, and finance, where privacy and integrity of voice traffic are critical.

Common Risks

  • Certificate Issues
    Invalid, expired, or self-signed certificates enable man-in-the-middle (MitM) attacks.
  • TLS Vulnerabilities
    Support for TLS 1.0/1.1 exposes systems to known exploits.
  • Authentication Weaknesses
    Encryption doesn’t mitigate risks from default or weak SIP credentials.
  • Resource Exhaustion
    TLS handshakes can be abused in denial-of-service (DoS) attacks.
  • Protocol Downgrade
    Improper fallback mechanisms could allow forced downgrade to unencrypted SIP.
  • Information Disclosure
    Misconfigured TLS or verbose banners may expose software versions and internal details.

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Enumeration & Testing

Check if it’s open:

Terminal window
nmap -sT -p 5061

Test TLS connection:

Terminal window
openssl s_client -connect :5061

SIP-TLS scan:

Terminal window
sipsak -T -s sip:test@:5061

What to Look For

CheckpointWhat it means
Weak SSL/TLS versionsVulnerable to attacks like POODLE, BEAST
Self-signed certificatesTrust issues, vulnerable to MitM
Registration enabledUnauthorized endpoints may register
Version informationMay reveal specific SIP or TLS stack used

Mitigation

  • Strong Encryption
    Enforce TLS 1.2 or higher, disable insecure cipher suites.
  • Valid Certificates
    Use trusted CA-signed certificates and monitor for expiry.
  • Authentication
    Require strong SIP credentials, consider MFA for admin tools.
  • Access Controls
    Restrict port 5061 access to known, trusted IP ranges.
  • Regular Updates
    Keep SIP server software and TLS libraries patched.

TL;DR

  • Port 5061 = SIP over TLS
  • Provides encrypted VoIP signaling
  • Common in secure communications infrastructure
  • Requires proper TLS configs, certificates, and auth controls

Known CVEs and Exploits

  • CVE-2023-28765 – DoS via malformed TLS handshake in SIP servers
  • CVE-2022-21702 – TLS certificate validation bypass in SIP proxy
  • CVE-2020-7491 – TLS downgrade vulnerability in VoIP products
  • CVE-2018-7284 – TLS certificate verification flaw in Cisco VoIP firmware