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CVE-2026-116783— FreeSWITCH mod_spandsp: out-of-bounds write parsing UDPTL error-recovery data

Quick assessment

Affected

signalwire freeswitch

Exploitation

No confirmed in-the-wild exploitation; assess based on exposure

Recommended action

Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

FreeSWITCH 是一个软件定义电信栈，旨在推动电信设备从专有交换机向可在任何通用硬件上运行的软件实现转型。在 1.11.2 版本之前，函数直接使用由对等端控制的 FEC（前向纠错）条目数量，来填充 mod_spandsp T.38 会话中的五条目 FEC 数组。若该数量过大，发送方可将错误恢复数据写入超出数组边界的内存区域，并将该过大的计数值保留，供后续的重建流程使用。任何能够向已建立的 T.38 传真会话发送 UDPTL（用户数据报传输层）的对等端均可触发此解析器，包括部署了传真应用或 T.38 网关的环

CVSS 8.2 · High Updated Nov 06, 2026

Possible ATT&CK Techniques 2 AI

T1069.004 T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

Vendor	Product	Version Range	Status
signalwire	freeswitch	`< 1.11.2`	affected

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Vulnerability Information

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Vulnerability Title

FreeSWITCH mod_spandsp: out-of-bounds write parsing UDPTL error-recovery data

Source: CVE Program / CVE List V5

Vulnerability 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, udptl_rx_packet() used a peer-controlled FEC entry count directly to fill five-entry FEC arrays in a mod_spandsp T.38 session. A larger count wrote sender-controlled error-recovery data beyond those arrays and persisted the oversized count for a later reconstruction pass. Any peer able to deliver UDPTL to an established T.38 fax session can reach the parser, including deployments using fax applications or a T.38 gateway. The memory corruption can crash FreeSWITCH and end every active call, although remote code execution has not been demonstrated. This issue is fixed in version 1.11.2.

Source: CVE Program / CVE List V5

CVSS Information

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

Source: CVE Program / CVE List V5

Vulnerability Type

对数组索引的验证不恰当

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
signalwire	freeswitch	< 1.11.2	-

II. Public POCs for CVE-2026-116783

#	POC Description	Source Link	Shenlong Link

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III. Intelligence Information for CVE-2026-116783

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Other References for CVE-2026-116783 (3)

https://github.com/signalwire/freeswitch/releases/tag/v1.11.2 x_refsource_MISC
https://github.com/signalwire/freeswitch/security/advisories/GHSA-mjp3-3cq2-hxj4 x_refsource_CONFIRM
https://github.com/signalwire/freeswitch/commit/b999d2a594f025ac0dd4d7b137635308ef298272 x_refsource_MISC

https://www.cve.org/CVERecord?id=CVE-2026-116783

Same Patch Batch · signalwire · 2026-11-05 · 21 CVEs total

CVE-2026-116779	9.8 CRITICAL	FreeSWITCH: Inbound SIP MESSAGE can select the api chat proto and run FreeSWITCH API comma
CVE-2026-116790	9.1 CRITICAL	FreeSWITCH: Inbound ICE connectivity checks are accepted without verifying STUN MESSAGE-IN
CVE-2026-116785	9.1 CRITICAL	FreeSWITCH: Pre-authentication heap out-of-bounds write in mod_xml_rpc WebSocket frame len
CVE-2026-116786	8.8 HIGH	FreeSWITCH: Channel-variable injection via SIP REFER leads to command execution in mod_sof
CVE-2026-116788	8.2 HIGH	FreeSWITCH: Pre-authentication heap buffer overflow in core XML empty-entity decoding
CVE-2026-116787	7.5 HIGH	FreeSWITCH: Pre-authentication process termination in the Event Socket via an unbounded Co
CVE-2026-116782	7.5 HIGH	FreeSWITCH: Pre-authentication invalid pointer dereference in mod_rtmp connect command han
CVE-2026-116784	7.5 HIGH	FreeSWITCH: Out-of-bounds read in RTCP NACK feedback parsing
CVE-2026-115928	7.5 HIGH	FreeSWITCH: Stack buffer overflow parsing the SDP a=crypto key material on inbound calls
CVE-2026-116570	7.5 HIGH	FreeSWITCH: Pre-authentication stack buffer overflow in mod_xml_rpc HTTP directory authent
CVE-2026-116567	7.5 HIGH	FreeSWITCH: Pre-authentication stack buffer overflow in mod_rtmp control-message handling
CVE-2026-116568	7.5 HIGH	FreeSWITCH: Out-of-bounds read in mod_rtmp H.264 video message parsing
CVE-2026-116569	7.5 HIGH	FreeSWITCH: Pre-authentication out-of-bounds write in MSRP message body parsing
CVE-2026-116789	7.4 HIGH	FreeSWITCH: DTLS-SRTP peer certificate is not bound to the SDP fingerprint when FreeSWITCH
CVE-2026-116573	6.5 MEDIUM	FreeSWITCH mod_sofia: stack buffer overflow from an over-long SIP To-header user
CVE-2026-116572	6.5 MEDIUM	FreeSWITCH mod_sofia: stack buffer overflow from an over-long SIP Contact display-name
CVE-2026-116571	5.9 MEDIUM	FreeSWITCH: Stack buffer overflow in mod_rtmp AVC sequence-header construction
CVE-2026-116574	5.9 MEDIUM	FreeSWITCH: Off-by-one heap write in core XML serialization of four-byte UTF-8 sequences
CVE-2026-116781	5.3 MEDIUM	FreeSWITCH: Pre-authentication out-of-bounds writes in mod_xml_rpc WebSocket frame parsing
CVE-2026-116780	2.7 LOW	FreeSWITCH: Heap out-of-bounds read in FreeSWITCH core variable expansion via `${variable:

IV. Related Vulnerabilities

Same product: freeswitch

Same vendor: signalwire

Same weakness: CWE-129