Malicious actors have been observed exploiting a now-patched critical security flaw impacting Erlang/Open Telecom Platform (OTP) SSH as early as beginning of May 2025, with about 70% of detections originating from firewalls protecting operational technology (OT) networks.

The vulnerability in question is CVE-2025–32433 (CVSS score: 10.0), a missing authentication issue that could be abused by an attacker with network access to an Erlang/OTP SSH server to execute arbitrary code. It was patched in April 2025 with versions OTP-27.3.3, OTP-26.2.5.11, and OTP-25.3.2.20.

Then in June 2025, the U.S. Cybersecurity and Infrastructure Security Agency (CISA) added the flaw to its Known Exploited Vulnerabilities (KEV) catalog, based on evidence of active exploitation.