by Kastro
Paper/Archive/CVE-2026-49840

CVE-2026-49840

signalwire freeswitch — FreeSWITCH: Pre-authentication heap buffer overflow in libesl `Content-Length` parsing

EPSS 0.3%CVSS 9.1
critical.is priorityof 100
32
CVSS 9.1 (CNA)9.1 / 10 × 3027.3Not in CISA KEV+300.0EPSS percentile 23.9.239 × 204.8No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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 version 1.11.1, esl_recv_event() parses Content-Length with atol() and passes the result straight to malloc(len + 1) with no sign or magnitude check. A malicious or man-in-the-middle ESL peer can send a frame with a negative Content-Length to corrupt the heap of, or crash, any process linked against libesl, before the client has authenticated to that peer. This issue has been patched in version 1.11.1.

Affected

ProductAffectedFixed inSource
freeswitch< 1.11.1–CNA

Scores by source

GitHub_M (CNA)9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: partial

References

refgithub.com/signalwire/freeswitch/security/advisories/GHSA-g597-9fgg-ghg9refgithub.com/signalwire/freeswitch/releases/tag/v1.11.1