Heap-based buffer overflow in freeswitch - CVE-2026-49840
Published: June 4, 2026
Vulnerability identifier: #VU133319
CSH Severity: High
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: CVE-2026-49840
CWE-ID: CWE-122
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: www.freeswitch.org
Affected software:
freeswitch
freeswitch
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service or corrupt heap memory.
The vulnerability exists due to a heap-based buffer overflow in libesl esl_recv_event() when parsing a crafted Content-Length header from an ESL peer. A remote attacker can send a specially crafted frame to cause a denial of service or corrupt heap memory.
The issue can be triggered before the client authenticates to the peer, and no credentials or prior interaction are required.
How to mitigate CVE-2026-49840
Install security update from vendor's website.