Vulnerability intelligence

CVE-2026-49840

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.

CVSS Score

9.1

Critical

EPSS — Exploit Probability

0.3%

Riskier than 24% of all CVEs · checked 2026-09-13

Exploitation

Not in CISA KEV

KEV does not include every exploited vulnerability

Remediation

Patch available

Vendor fix published