Horizon Alert
Summary of the vulnerability and why it matters
This vulnerability in Erlang/OTP's TLS client could allow an attacker to intercept and modify communications by tricking the client into using an insecure, anonymous cipher suite. While this impacts older TLS versions and DTLS, it does not affect TLS 1.3. The primary concern is determining if your organization utilizes affected versions and is susceptible to this type of man-in-the-middle attack.
- Client TLS misconfigures cipher suites, enabling snooping.
- Protects against unauthorized data access and tampering.
- Confirm relevance and check for potential exposure.
Attack Path
How an attacker could exploit the issue
An attacker positioned between a vulnerable Erlang/OTP client and its intended server can trick the client into accepting an anonymous cipher suite. This bypasses certificate validation, allowing the attacker to establish a seemingly legitimate connection. The attacker can then read and alter all subsequent communication between the client and the server.
- An on-path attacker is required.
- Client accepts unoffered anonymous cipher suite.
- All subsequent traffic is readable and modifiable.
Live Threat
Current exploitation, exposure, and threat context
When supported by the advisory, an on-path attacker could cause a TLS 1.2 or earlier client to accept an anonymous cipher suite during the handshake. This bypasses server certificate validation, allowing the attacker to read and modify all subsequent application traffic between the client and the intended server.
- Data in transit could be exposed.
- Attacker intercepts and manipulates traffic.
- Application traffic becomes readable and modifiable.
Operational Fix
Recommended remediation, mitigation, and detection steps
This vulnerability affects Erlang/OTP TLS clients that do not verify cipher suite negotiation, allowing an on-path attacker to intercept and modify application traffic. Identifying affected systems, confirming their reachability and criticality, and then engaging the accountable owner are the first practical steps. Remediation planning should be risk-based.
- Application owners or platform teams should own remediation.
- Verify TLS 1.3 usage and affected component reachability.
- Plan and coordinate risk-based remediation or mitigation.
