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.

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

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

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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.