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CVE

CVE-2026-49840

FreeSWITCH: Pre-authentication heap buffer overflow in libesl `Content-Length` parsing
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CVE

CVE-2026-49840

FreeSWITCH: Pre-authentication heap buffer overflow in libesl `Content-Length` parsing

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, eslrecvevent() 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.

Package Versions Affected

Package Version
patch Availability
No items found.

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CVSS Version

Severity
Base Score
CVSS Version
Score Vector
C
H
U
9.1
-
3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
C
H
U
0
-
3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
C
H
U
-

Related Resources

No items found.

References

https://github.com/signalwire/freeswitch/releases/tag/v1.11.1, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/49xxx/CVE-2026-49840.json, https://github.com/signalwire/freeswitch/security/advisories/GHSA-g597-9fgg-ghg9, https://nvd.nist.gov/vuln/detail/CVE-2026-49840

Severity

9.1

CVSS Score
0
10

Basic Information

Base CVSS
9.1
EPSS Probability
0.0031%
EPSS Percentile
0.23097%
Introduced Version
0
Fix Available
c2c59645f6911a76589e5008c4d73349ded44b65,1.11.1

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