Is CVE-2026-49840 in the CISA KEV catalog?

No. CVE-2026-49840 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-49840?

CVE-2026-49840 has a CVSS v3 base score of 9.1 (CRITICAL).

What is the EPSS score for CVE-2026-49840?

CVE-2026-49840 has an EPSS score of 0.31% (23th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-49840?

Upgrade freeswitch to 1.11.1 or later.

CVE & CISA-KEV Catalog

CVE-2026-49840

CRITICAL

9.1

CVSS v3

NVD

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.

CWE-20Improper Input Validation CWE-122Heap-based Buffer Overflow CWE-195 CWE-787Out-of-bounds Write

How to fix

Remediation Available

freeswitchNVD

Affected:< 1.11.1Fixed in:1.11.1CVE-2026-49840derived from NVD

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

0.31%probability of exploitation in 30 days

23rdpercentile

Low risk: more likely to be exploited than 23% of all known CVEs.

References

Third-Party Advisory1

github.com

Release Notes1

github.com

Related Vulnerabilities

Other CWE-20 (Improper Input Validation) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2024-3400	Critical	10.0	100%	KEV + Ransom	-
CVE-2021-45105	Medium	5.9	100%	-	Fix
CVE-2021-44228	Critical	10.0	100%	KEV + Ransom	Fix
CVE-2021-21985	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2018-7600	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2020-3452	High	7.5	100%	KEV	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-10.