CVE-2026-116785: FreeSWITCH: Pre-authentication heap out-of-bounds write in mod_xml_rpc WebSocket frame length handling

Vulnerability summary

CVE-2026-116785 is a critical (CVSS 9.1) Heap-based Buffer Overflow vulnerability in signalwire freeswitch. EPSS estimates a 1.03% chance of exploitation in the next 30 days, higher than 64% of scored vulnerabilities.

Timeline

1. 05-11-2026
   PublishedVulnerability first disclosed.
2. 09-11-2026
   Last modifiedVulnerability information updated.

Description

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, ws_read_frame() decoded a WebSocket frame's 64-bit extended payload length with a 32-bit byte swap and narrowed the result into a signed length. A value whose surviving low word became negative bypassed the signed size check and was reinterpreted as an enormous unsigned count, causing client bytes to overwrite memory beyond the 64 KiB receive buffer. Any client completing a /socket WebSocket upgrade on an enabled mod_xml_rpc endpoint reached the parser before HTTP authentication; both the module and WebSocket endpoint are disabled by default. The heap overwrite can corrupt connection pointers and crash FreeSWITCH, ending every concurrent session, although remote code execution has not been demonstrated. This issue is fixed in version 1.11.2.

• CWE-122Heap-based Buffer OverflowThe product writes past the end of a buffer that was allocated on the heap.
• CWE-681Incorrect Conversion between Numeric TypesWhen converting from one data type to another, such as long to integer, data can be omitted or translated in a way that produces unexpected values. If the resulting values are used in a sensitive context, then dangerous behaviors may occur.
• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.