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CVE-2026-49840

Freeswitch buffer overflow

9.1 CRITICALEPSS 0.48%
  1. Published9 Jun 2026

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 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Affected products

Freeswitch< 1.11.1

Remediation

Fixed in
Freeswitch≥ 1.11.1

References

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Frequently asked

Is CVE-2026-49840 being actively exploited?

CVE-2026-49840 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.48%.

How severe is CVE-2026-49840?

CVE-2026-49840 has a CVSS 3.1 base score of 9.1, rated critical. EPSS estimates a 0.48% probability of exploitation.

Which products are affected by CVE-2026-49840?

Affected products include Freeswitch.

How do I fix CVE-2026-49840?

Upgrade affected software to a fixed version, for example Freeswitch 1.11.1 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-49840 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.