# CVE-2026-116574: FreeSWITCH: Off-by-one heap write in core XML serialization of four-byte UTF-8 sequences

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, switch_xml_ampencode() reserved only ten bytes for the widest numeric character reference produced from a four-byte UTF-8 sequence, omitting space for the terminating NUL. When remote-supplied text was serialized at the exact buffer-growth boundary, the terminator wrote one byte beyond the heap allocation. Reachable surfaces include mod_xml_cdr, conference and formatted CDR XML, XML Event Socket output, and XML API output that serializes caller-controlled values. The fixed zero-byte write can abort the process or truncate an adjacent object, while remote 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:L/UI:N/S:U/C:N/I:L/A:H; source: CNA: GitHub_M

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

- CISA KEV: No listing in collected sources

- EPSS: 0.38% as of 2026-11-09; percentile 32.14%

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

- Weaknesses: CWE-193, CWE-787

## Exploit evidence

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

## References

- https://github.com/signalwire/freeswitch/security/advisories/GHSA-r6vh-qmwm-h3cc (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/signalwire/freeswitch/commit/28fcfd26246c112fa4b9e698433d09e4836ca1b5 (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/28fcfd26246c112fa4b9e698433d09e4836ca1b5 (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-r6vh-qmwm-h3cc (security-advisories@github.com)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-116574; retrieved 2026-11-09; source updated 2026-11-09

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-116574; retrieved 2026-11-10; source updated 2026-11-09

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-116574; retrieved 2026-11-09; source updated Not reported

Revision: 89585c46fb2ce3994eb6cb83a84f1962b965d5125d8713e4222e955c3b992574

Canonical: https://y2.dev/cve/CVE-2026-116574

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