CVE-2026-116567: FreeSWITCH: Pre-authentication stack buffer overflow in mod_rtmp control-message handling

Vulnerability summary

CVE-2026-116567 is a high (CVSS 7.5) Stack-based Buffer Overflow vulnerability in signalwire freeswitch. EPSS estimates a 0.43% chance of exploitation in the next 30 days, higher than 37.7% of scored vulnerabilities.

Timeline

1. 05-11-2026
   PublishedVulnerability first disclosed.
2. 09-11-2026
   Last modifiedVulnerability information updated.

Description

FreeSWITCH is a Software Defined Telecom Stack enabling the digital transformation from proprietary telecom switches to a software implementation that runs on any commodity hardware. Prior to 1.11.2, rtmp_handle_control() rendered an RTMP user-control message into a 200-byte stack buffer using an unbounded sprintf loop controlled by the wire message length. A body of roughly 70 bytes or more overflowed the stack before any RTMP login, because the handshake authenticates neither side. The flaw affects deployments that build and load mod_rtmp, which is disabled in the stock build and configuration but commonly exposes a listener on TCP port 1935 when enabled. One unauthenticated message can crash FreeSWITCH and end every active call; the constrained ASCII hex output has not yielded control-flow hijacking. This issue is fixed in version 1.11.2.

• CWE-121Stack-based Buffer OverflowThe product writes past the end of a buffer that was allocated on the stack.