SignalWire FreeSWITCH up to 1.11.1 Channel-Variable Expander switch_event_expand_headers_check variable:offset heap-based overflow

Summaryinfo

A vulnerability was found in SignalWire FreeSWITCH up to 1.11.1. It has been classified as very critical. Affected is the function switch_event_expand_headers_check of the component Channel-Variable Expander. The manipulation of the argument variable:offset leads to heap-based overflow. This vulnerability is traded as CVE-2026-116780. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in SignalWire FreeSWITCH up to 1.11.1. It has been rated as very critical. This issue affects the function switch_event_expand_headers_check of the component Channel-Variable Expander. The manipulation of the argument variable:offset with an unknown input leads to a heap-based overflow vulnerability. Using CWE to declare the problem leads to CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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_event_expand_headers_check() advanced beyond its heap copy when a positive offset in ${variable:offset} exceeded the variable value's length. The following length calculation and copy appended adjacent heap memory to the expansion result, potentially exposing channel variables, credentials, allocator data, and pointer bytes. The flaw is reachable through configuration templates that slice remote input and through authenticated Event Socket eval or Event Socket expand commands; the separate channel-variable expander used by ordinary dialplan slicing is unaffected. The requester cannot choose adjacent memory and disclosure stops at a zero byte, but repeated expansion can influence the layout. This issue is fixed in version 1.11.2.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-116780 since 10/26/2026. The exploitation is known to be easy. The attack may be initiated remotely. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 11/05/2026).

Upgrading to version 1.11.2 eliminates this vulnerability.

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Productinfo

Vendor

• SignalWire

Name

• FreeSWITCH

Version

• 1.11.0
• 1.11.1

Website

• Product: https://github.com/signalwire/freeswitch/

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