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

Status: published. Published: 2026-11-05. Updated: 2026-11-09.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- signalwire / freeswitch: < 1.11.2 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 3.1: 5.9 (medium); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: GitHub_M

- CVSS 3.1: 5.9 (medium); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: security-advisories@github.com

- CISA KEV: No listing in collected sources

- EPSS: 0.37% as of 2026-11-09; percentile 31.55%

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-121

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/signalwire/freeswitch/security/advisories/GHSA-qmh2-f6cv-79mf (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/signalwire/freeswitch/commit/2ab0a534fdc25301daf95590e90a756a76bf0950 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/signalwire/freeswitch/releases/tag/v1.11.2 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/signalwire/freeswitch/commit/2ab0a534fdc25301daf95590e90a756a76bf0950 (security-advisories@github.com)

- https://github.com/signalwire/freeswitch/releases/tag/v1.11.2 (security-advisories@github.com)

- https://github.com/signalwire/freeswitch/security/advisories/GHSA-qmh2-f6cv-79mf (security-advisories@github.com)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-116571; retrieved 2026-11-09; source updated 2026-11-09

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-116571; retrieved 2026-11-06; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-116571; retrieved 2026-11-09; source updated Not reported

Revision: 47afbd0192cbdf2896b0c4994e6c6003a7a960361ecd447fec39041e23257605

Canonical: https://y2.dev/cve/CVE-2026-116571

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