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

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Summary

CVECVE-2026-49840
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-09 17:17:47 UTC
Updated2026-06-10 15:06:24 UTC
DescriptionFreeSWITCH 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.

Risk And Classification

Primary CVSS: v3.1 9.1 CRITICAL from [email protected]

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

Problem Types: CWE-20 | CWE-122 | CWE-195 | CWE-787 | CWE-20 CWE-20: Improper Input Validation | CWE-122 CWE-122: Heap-based Buffer Overflow | CWE-195 CWE-195: Signed to Unsigned Conversion Error | CWE-787 CWE-787: Out-of-bounds Write

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
3.1CNADECLARED9.1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
High

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Freeswitch Freeswitch All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Signalwire Freeswitch affected < 1.11.1 Not specified

References

ReferenceSourceLinkTags
github.com/signalwire/freeswitch/security/advisories/GHSA-g597-9fgg-ghg9 [email protected] github.com Third Party Advisory
github.com/signalwire/freeswitch/releases/tag/v1.11.1 [email protected] github.com Release Notes
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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