CVE-2026-116571: FreeSWITCH: Stack buffer overflow in mod_rtmp AVC sequence-header construction
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, rtmprtp2rtmpH264() 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 modrtmp 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.
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
FreeSWITCHto a version that resolves this vulnerability.Fixed in 1.11.2
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Only deployments that build and load mod_rtmp and bridge RTP media into an RTMP leg are affected. The module is disabled in the stock build and configuration.
What must an attacker control to trigger the overflow?
An established H.264 call must be bridged toward an RTMP endpoint, and the attacker must supply oversized SPS and PPS parameter sets in the media stream. The attack is network-reachable but has high complexity.
What is the likely operational impact?
Memory corruption can abort FreeSWITCH and terminate every active call. On builds without stack protection, the issue provides a limited stack-write primitive, although code execution has not been demonstrated.
What should teams do if they cannot upgrade immediately?
Disable or avoid loading mod_rtmp and avoid bridging RTP media into RTMP legs until the deployment can be updated. The issue is fixed in FreeSWITCH 1.11.2.