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FreeswitchApplication

CVE-2026-49847

HIGH · 7.5 CVSS v3.1 Published 2026-06-09
Fix available
A fix is available. Upgrade to 1.11.1 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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, a single unauthenticated WebSocket frame containing a deeply nested JSON document crashes the FreeSWITCH process via stack overflow, terminating all calls and sessions on the host. The recursion drives the worker thread's stack pointer into the stack guard page, raising SIGSEGV from the kernel before any usable write primitive develops. This issue has been patched in version 1.11.1.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

FreeSWITCH versions prior to 1.11.1 contain a stack overflow vulnerability in their WebSocket handling implementation. An unauthenticated attacker can send a single WebSocket frame containing a deeply nested JSON document, which triggers excessive recursion during parsing. This causes the worker thread's stack pointer to exceed the stack guard page, resulting in a SIGSEGV signal that terminates the FreeSWITCH process and all active calls/sessions.

MitigationUpgrade FreeSWITCH to version 1.11.1 or later. As a temporary workaround, implement network-level filtering to restrict unauthenticated WebSocket connections or deploy a WAF capable of detecting and blocking abnormally nested JSON payloads.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FreeswitchApplication
Affected:< 1.11.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed FreeSWITCH version
    Run 'freeswitch -version' or check the package version installed via your package manager (dpkg -r, rpm -qi, etc.)
    Affected if The version is lower than 1.11.1
  2. Verify WebSocket module is loaded
    Check FreeSWITCH configuration files (autoload_configs/modules.conf.xml) for 'mod_websockets' entry or run 'fs_cli -x "module list"' to see loaded modules
    Affected if mod_websockets is loaded and enabled
  3. Confirm WebSocket endpoint is configured and exposed
    Inspect sip_profiles or the specific WebSocket configuration for any 'ws://' or 'wss://' listeners. Check for lines containing 'websocket' in the SIP profile XML files under /etc/freeswitch/sip_profiles/
    Affected if A WebSocket listener is configured and bound to an accessible IP/port
  4. Check network exposure of WebSocket service
    Review firewall rules or network ACLs to determine if the WebSocket port (typically 8080 or 7443 for WSS) is accessible from untrusted networks
    Affected if The WebSocket port is open to unauthenticated/untrusted network access

If your FreeSWITCH version is below 1.11.1 AND the WebSocket module is loaded and exposed to the network, you are affected by this vulnerability.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.11.1 or later
Fixed in 1.11.1
Interim mitigation

Upgrade FreeSWITCH to version 1.11.1 or later. As a temporary workaround, implement network-level filtering to restrict unauthenticated WebSocket connections or deploy a WAF capable of detecting and blocking abnormally nested JSON payloads.

Recommended fix High confidence

FreeSWITCH 1.11.1

  1. Verify current FreeSWITCH version by running 'fs_cli -x "version"' or checking the process version
  2. Stop the FreeSWITCH service gracefully using 'systemctl stop freeswitch' or 'freeswitch -stop'
  3. Backup the current FreeSWITCH configuration directory (typically /etc/freeswitch) and any custom modules or scripts
  4. Update the package repository and install FreeSWITCH version 1.11.1 using the appropriate package manager (e.g., 'apt-get update && apt-get install freeswitch=1.11.1' or compile from source using the 1.11.1 tag from the official Git repository)
  5. Verify the upgrade by running 'fs_cli -x "version"' and confirming it shows 1.11.1
  6. Start the FreeSWITCH service using 'systemctl start freeswitch' or 'freeswitch'
  7. Test WebSocket functionality by establishing a test WebSocket connection and sending a non-malformed JSON message to confirm normal operation
Caveat Minor: Review release notes for 1.11.1 for any behavioral changes; some modules or configurations may require adjustment if deprecated features were removed

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Freeswitch Scoped from the published advisory
  • Consultation4.0 h
  • Implementation6.0 h
  • Testing8.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,800
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-49847 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data