# CVE-2026-49847: FreeSWITCH stack overflow in cJSON parser via mod_verto

Source: https://junglewise.ai/threats/cve-2026-49847-freeswitch-stack-overflow-in-cjson-parser-via-mod-verto  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-09. Updated: 2026-06-09  
License: CC BY 4.0 with a link back

CVE-2026-49847 · Severity: high · CVSS 7.5 · Published 2026-06-09

FreeSWITCH is an open-source telephony platform used to manage voice, video, and messaging communications. A vulnerability in how the system processes certain data formats allows an unauthenticated remote attacker to crash the entire service by sending a single malicious message. This results in a total service outage, immediately terminating all active phone calls and communication sessions on the affected server.

Technologies: [SignalWire FreeSWITCH](https://junglewise.ai/threats/technologies/freeswitch). Vendors: [SignalWire](https://junglewise.ai/threats/vendors/signalwire).

## Quick answers

**Is CVE-2026-49847 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-49847 being exploited in the wild.

**How severe is CVE-2026-49847?** High severity, with a CVSS score of 7.5, published 9 June 2026.

**Which products and versions are affected?** SignalWire FreeSWITCH < 1.11.1.

**Is there a fix for CVE-2026-49847?** A patch was published on 2026-05-26: Version 1.11.1 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-49847 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-49847?** Check whether you run SignalWire FreeSWITCH at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

FreeSWITCH contains an uncontrolled recursion vulnerability in its bundled cJSON parser. The parser uses recursive descent to process JSON objects and arrays; however, the default nesting limit exceeds the available stack size (240 KiB) of the FreeSWITCH worker threads. An unauthenticated attacker can send a specially crafted, deeply nested JSON document via a mod_verto WebSocket frame (typically on ports 8081 or 8082) to trigger a stack overflow. This results in a SIGSEGV (segmentation fault) that crashes the FreeSWITCH process before authentication occurs. The issue is fixed in version 1.11.1 by capping the CJSON_NESTING_LIMIT to 64.

## Affected products

- SignalWire FreeSWITCH < 1.11.1

## Timeline

- 2026-05-26: patched: Version 1.11.1 released
- 2026-06-03: advisory: GitHub Security Advisory published
- 2026-06-09: disclosed: CVE published to NVD

## References

- [https://github.com/signalwire/freeswitch/releases/tag/v1.11.1](https://github.com/signalwire/freeswitch/releases/tag/v1.11.1)
- [https://github.com/signalwire/freeswitch/security/advisories/GHSA-2v74-pcgh-75wg](https://github.com/signalwire/freeswitch/security/advisories/GHSA-2v74-pcgh-75wg)

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