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

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_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.

## Remediation

- fix: FreeSWITCH (c): GitHub reports patched versions >= 1.11.2. Check the advisory for the affected release branch. (source: GitHub GHSA-hj6x-9653-p796) — https://github.com/signalwire/freeswitch/security/advisories/GHSA-hj6x-9653-p796

## Affected products and versions

- signalwire / freeswitch: < 1.11.2 (affected). Source: CNA: GitHub_M
-  / FreeSWITCH (FreeSWITCH): <= 1.11.1 (affected, GitHub advisory range). Source: GitHub GHSA-hj6x-9653-p796

## Severity and prioritization

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: GitHub_M

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/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: 0.43% as of 2026-11-09; percentile 37.67%

- SSVC: exploitation none; automatable yes; technical impact partial; 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-hj6x-9653-p796 (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/signalwire/freeswitch/commit/fc0db829b87d1a5a3043e355b4294c41851b13c6 (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/fc0db829b87d1a5a3043e355b4294c41851b13c6 (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-hj6x-9653-p796 (security-advisories@github.com)

- https://github.com/signalwire/freeswitch/security/advisories/GHSA-hj6x-9653-p796 (GitHub Security Advisories; advisory)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-116567; retrieved 2026-11-09; source updated 2026-11-09

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-116567; retrieved 2026-11-06; source updated 2026-11-05

- GitHub Security Advisories: https://github.com/signalwire/freeswitch/security/advisories/GHSA-hj6x-9653-p796; retrieved 2026-11-07; source updated 2026-10-26

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-116567; retrieved 2026-11-09; source updated Not reported

Revision: 58c0e45ad537f43bfcb0861359fa08b3174cf5cd3fcef92c476ba70d9fe3c658

Canonical: https://y2.dev/cve/CVE-2026-116567

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