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 23% of all CVEs

Exploitation

Not in CISA KEV

No federal exploitation record

Remediation

Patch available

Vendor fix published

NVD entry Vendor patch PoC / advisory

1 article across 1 outlet · first covered Jun 16, 2026 · latest Jun 16, 2026

Coverage timeline

FreeSWITCH bugs allow remote code exec without auth, urgent patch
securityonline.info · Jun 16, 2026