Bug 2567820 (CVE-2026-116783)

Summary: CVE-2026-116783 freeswitch: freeswitch: Denial of Service via buffer overflow in T.38 UDPTL packet processing
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in FreeSWITCH. A remote attacker can trigger memory corruption leading to a Denial of Service (DoS) by sending specially crafted UDP Transport Layer (UDPTL) packets to an established T.38 fax session. Because the service does not properly validate peer-controlled Forward Error Correction (FEC) entry counts, incoming data is written beyond fixed memory boundaries. Successful exploitation crashes the FreeSWITCH application, terminating all active calls.
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Description OSIDB Bzimport 2026-11-05 22:28:27 UTC 
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.