CVE-2026-49840
FreeSWITCH: Pre-authentication heap buffer overflow in libesl `Content-Length` parsing
CVSS Score
9.1
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-20 CWE-122 CWE-195 CWE-787 |
| Vendor | signalwire |
| Product | freeswitch |
| Published | Jun 9, 2026 |
| Last Updated | Jun 9, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
High
Affected Versions
signalwire / freeswitch
< 1.11.1