CVE-2026-116571: FreeSWITCH: Stack buffer overflow in mod_rtmp AVC sequence-header construction

Vulnerability summary

CVE-2026-116571 is a medium (CVSS 5.9) Stack-based Buffer Overflow vulnerability in signalwire freeswitch. EPSS estimates a 0.37% chance of exploitation in the next 30 days, higher than 31.5% 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_rtp2rtmpH264() built an AVC decoder configuration record in a fixed stack buffer by copying wire-derived SPS and PPS values without checking that their sizes and framing fit. An established H.264 call bridged toward an RTMP endpoint could supply oversized SPS and PPS parameter sets and overrun the function's stack frame. The flaw affects only deployments that build and load mod_rtmp and bridge RTP media into an RTMP leg; the module is disabled in the stock build and configuration. The corruption can abort FreeSWITCH and terminate every active call, and builds without stack protection receive a limited stack-write primitive, although code execution has not been demonstrated. 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.