---
cve: "CVE-2026-49840"
severity: "CRITICAL"
cvss: 9.1
epss: "0.3%"
vendor: "signalwire"
kev: false
exploited: false
published: "2026-06-09 17:17:47"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-11-09T15:01:53+01:00"
---

# CVE-2026-49840

> 9.1 CRITICAL · 🧪 PoC

## Beschreibung

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.

## CNA-Record (Kanon, cvelistV5)

- CNA: **GitHub_M**
- State: PUBLISHED
- Stand: 2026-06-09 17:00:21
- CNA-CVSS: **9.1** (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **none**
  - Automatable: **yes**
  - Technical Impact: **partial**

## CVSS-Vektor

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

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Keine | good |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Schwachstellen-Klasse

- **CWE-122** — Heap-based Buffer Overflow
  The product writes past the end of a buffer that was allocated on the heap.
- **CWE-195** — Signed to Unsigned Conversion Error
  The product uses a signed primitive and performs a cast to an unsigned primitive, which can produce an unexpected value if the value of the signed primitive can not be represented using an unsigned primitive.
- **CWE-20** — Improper Input Validation
  The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
- **CWE-787** — Out-of-bounds Write
  The product writes data past the end, or before the beginning, of the intended buffer.

## Angriffsmuster (CAPEC)

- [CAPEC-92 — Forced Integer Overflow](https://capec.mitre.org/data/definitions/92.html) _(Severity: High)_

## Patch verfügbar (OSV)

- c2c59645f6911a76589e5008c4d73349ded44b65 (Commit)

## Referenzen

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

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-49840/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_