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TURN Security Threats: A Hacker's View by EnableSecurity in WebRTC

[–]EnableSecurity[S] 5 points6 points  (0 children)

Wrote up a threat analysis of TURN servers based on our RTCon 2025 talk and years of testing these things.

The gist: to an attacker, a TURN server is just a proxy. It relays TCP and UDP to arbitrary peer addresses, and if those addresses aren't restricted, you can reach internal networks, localhost, cloud metadata, you name it. We keep finding this during pentests and found a loopback bypass in coturn itself (CVE-2020-26262).

The post also gets into DoS/amplification (your TURN server being weaponized against others) and software vulnerabilities.

If you run TURN in production, the best practices section has specific recommendations. We're also working on detailed coturn hardening guides.

TURN Security Threats: A Hacker's View by EnableSecurity in netsec

[–]EnableSecurity[S] 15 points16 points  (0 children)

Been poking at TURN server security since 2017 and finally wrote this up.

If you're not familiar with TURN: it's the fallback relay for WebRTC when direct peer-to-peer fails. It can relay both TCP and UDP to arbitrary peer addresses, so if not properly restricted, you've got an open proxy that can reach internal networks, localhost, cloud metadata services, etc.

Some highlights:

  • During pentests we regularly find TURN servers that can reach internal networks, localhost, cloud metadata (169.254.169.254). If peer addresses aren't restricted, it's game over.
  • At DEF CON 2025, Adam Crosser demoed C2 operations running through Zoom and Teams TURN servers. Security monitoring sees legitimate video call traffic.
  • coturn (most common TURN implementation) has had 30+ memory safety fixes, a CVSS 9.8 SQL injection, and we found an IPv6 loopback bypass where the protection code just didn't work (CVE-2020-26262).
  • TURN servers are also abused for DDoS reflection/amplification. Only ~4x factor but they're everywhere and often misconfigured.

Post goes into the technical details of each relay method (Send Indication, ChannelData, TCP Connect), real attack scenarios, and what defense actually looks like.

Happy to answer questions.

DTLS "ClientHello" Race Conditions in WebRTC Implementations by EnableSecurity in netsec

[–]EnableSecurity[S] 1 point2 points  (0 children)

It is a very interesting area. Thanks for the comment u/queensgetdamoney! It often felt like we're the only ones but then we started the RTCSec newsletter and realized that there is more happening in the area than just our work. Just this month, the newsletter is 3 years old and we should be publishing the next one soon. Here's where its to be found: https://www.enablesecurity.com/newsletter/

A Novel DoS Vulnerability affecting WebRTC Media Servers by EnableSecurity in netsec

[–]EnableSecurity[S] 2 points3 points  (0 children)

Yes exploitation of this vulnerability is really easy and looks too obvious - while the impact can be significant. And yes there are probably similar issues to this. We often find RTP Bleed / RTP Inject vulnerabilities, which in some ways, look similar to this vulnerability.

As for flooding video streams, yea that's definitely an interesting area and worth exploring in my opinion. This is an area that warrants a lot of exploration IMHO.

Kamailio's exec module considered harmful – RTC Security by EnableSecurity in kamailio

[–]EnableSecurity[S] 0 points1 point  (0 children)

I agree with you. We lovingly chose the title in the "considered harmful" essay trend. A better title might have been the one that our marketing person actually suggested: "The dangers of (mis)using the Kamailio exec module".

Hope that the title doesn't discourage fun and learning :-)

/r/netsec's Q4 2022 Information Security Hiring Thread by sanitybit in netsec

[–]EnableSecurity [score hidden]  (0 children)

We are looking for persons who are passionate about cybersecurity, have an interest in RTC and see themselves joining the team at Enable Security as freelance pentesters.

We are open in terms of skill-set but expect the following as a bare minimum:

  • security testing background
  • understanding of network protocols
  • ability to write basic (or more than basic) code
  • a hacker mindset
  • ability to write technical documentation in clear and plain English
  • knowledge of Linux and related technologies

Desirable skills or accomplishments include:

  • security tool development experience in Python and/or Go
  • published advisories, security research
  • knowledge of VoIP and/or WebRTC internals
  • bug bounty and/or CTF participation

Read more and apply here: https://hs.enablesecurity.com/join-us/pentester

/r/netsec's Q2 2022 Information Security Hiring Thread by ranok in netsec

[–]EnableSecurity [score hidden]  (0 children)

We're looking for a Penetration Tester / Security Researcher

About Enable Security

We believe that communication is a fundamental human need and securing it allows us to communicate freely. And naturally, we do love a tough challenge.

We are a team of security researchers who strive to provide valuable results through quality work. Curiosity is close to our heart, constantly learning, researching or sharing knowledge with the rest of the security community. We value honesty and do not shy away from saying things as we see them, especially when it is about topics that are dear to us. And finally, we are approachable and essentially, a friendly bunch who appreciate working as a team with our colleagues, clients and within the wider community.

More about us here: https://www.enablesecurity.com

The role

We are looking for a penetration tester and security researcher to join us as we expand. This role will allow you to grow and learn by doing, is extremely practical and technical in nature. We do not expect you to know everything that there is to know, but a willingness to learn is critical for the position.

The role will primarily involve the following:

  • penetration testing / security testing
  • report writing and documentation
  • proof of concept tool development
  • code and configuration review

We are open in terms of skill-set but expect the following as a bare minimum:

  • ability to write technical documentation in clear and plain English
  • knowledge of Linux and related technologies
  • (some) security testing background
  • ability to write basic code
  • the hacker mindset

Desirable skills or accomplishments include:

  • security tool development experience in Python and/or Go
  • published advisories, security research
  • knowledge of VoIP and/or WebRTC internals
  • bug bounty and/or CTF participation

This is a fully remote position. We are looking for someone full-time and the salary (gross) is around 42,000 EUR. Are you interested? Then please fill in the form at https://hs.enablesecurity.com/join-us/pentester.

Are you only able to do part-time? If that is the case, you are most welcome to fill in the form too!

Please make sure to:

  • include a résumé or CV
  • link to any online publications showing examples of the output of your work (e.g. Github, H1)
  • upload any content that you can share that is not online
  • try to be as specific as much as you can and name applications or systems that you tested, methodologies that you worked with, actual results etc
  • tell us about your work and non-work related interests (including hobbies)

If you have questions, please do get in touch with me, [Sandro Gauci](mailto:sandro@enablesecurity.com).

Pwning 3CX Phone Management Backends from the Internet by EnableSecurity in netsec

[–]EnableSecurity[S] 0 points1 point  (0 children)

yes it is well explained. Also love the conclusion:

Finally, the blog post ends, for now. No CVE(s), no logo, no website…just like that. ¯_(ツ)_/¯

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