CVE-2026-49840

Description

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 v3.1 Score

9.1

CRITICAL

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

EPSS — Exploit Prediction

0.0031

Probability of exploitation

0.23%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-20 Improper Input Validation

CWE-122 CWE-122

CWE-195 CWE-195

CWE-787 Out-of-bounds Write

Affected Products

Vendor	Product	Versions
freeswitch	freeswitch	< 1.11.1

References

Other References

https://github.com/signalwire/freeswitch/releases/tag/v1.11.1 https://github.com/signalwire/freeswitch/security/advisories/GHSA-g597-9fgg-ghg9

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-49840? +

CVE-2026-49840 has a CVSS v3.1 score of 9.1 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0031, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-49840? +

CVE-2026-49840 affects products from freeswitch, specifically: freeswitch. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-49840? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2025-13826

Zervit's portable HTTP/web server is vulnerable to remote DoS attacks when a configuration reset request is made. The vulnerability is …

CVE-2024-54011

Penetration Testing engineers at Amazon have discovered a flaw where the camera system fails to properly handle data supplied in …

CVE-2026-6409

A Denial of Service (DoS) vulnerability exists in the Protobuf PHP library during the parsing of untrusted input. Maliciously structured …

CVE-2026-12569

A critical remote code execution (RCE) vulnerability has been reported in PTC Windchill PDMlink and PTC FlexPLM. The vulnerability may …

CVE-2025-23202

Bible Module is a tool designed for ROBLOX developers to integrate Bible functionality into their games. The `FetchVerse` and `FetchPassage` …

CVE-2025-24501

An improper input validation allows an unauthenticated attacker to alter PAM logs by sending a specially crafted HTTP request.