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FreeswitchApplication

CVE-2021-41157

MEDIUM · 5.3 CVSS v3.1 Published 2021-10-26
Fix available
A fix is available. Upgrade to 1.10.6 or later.
See remediation →
62/100
Remediation priority · Elevated
Public exploit Remotely reachable No privileges Zero-click Patch available

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. By default, SIP requests of the type SUBSCRIBE are not authenticated in the affected versions of FreeSWITCH. Abuse of this security issue allows attackers to subscribe to user agent event notifications without the need to authenticate. This abuse poses privacy concerns and might lead to social engineering or similar attacks. For example, attackers may be able to monitor the status of target SIP extensions. Although this issue was fixed in version v1.10.6, installations upgraded to the fixed version of FreeSWITCH from an older version, may still be vulnerable if the configuration is not updated accordingly. Software upgrades do not update the configuration by default. SIP SUBSCRIBE messages should be authenticated by default so that FreeSWITCH administrators do not need to explicitly set the `auth-subscriptions` parameter. When following such a recommendation, a new parameter can be introduced to explicitly disable authentication.

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
How this class of weakness works · CWE-287

The mechanism that verifies who a user is can be side-stepped or fooled, letting an attacker act as someone they're not. Everything built on top of that identity then becomes untrustworthy. Fixing it means hardening the full authentication flow, including edge cases, tokens, and secondary paths.

General guidance for the improper authentication class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

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:< 1.10.6

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
Low
Integrity
None
Availability
None

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

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 1.10.6 or later
Fixed in 1.10.6
Vendor patch github.com →
Recommended fix High confidence

FreeSWITCH v1.10.6

  1. Upgrade FreeSWITCH to version 1.10.6 or later
  2. Locate the FreeSWITCH SIP profile configuration file (typically in /etc/freeswitch/sip_profiles/ or within the dialplan configuration)
  3. Add or verify the parameter `auth-subscriptions` is set to `true` in the SIP profile settings
  4. If using an older configuration file structure, add the parameter `<param name="auth-subscriptions" value="true"/>` inside the relevant SIP profile section
  5. Restart FreeSWITCH service or execute `fs_cli -x "reloadxml"` to apply configuration changes
  6. Verify that SIP SUBSCRIBE requests now require authentication by testing with an unauthenticated SUBSCRIBE message
Caveat Configuration file changes do not auto-migrate on upgrade; manual configuration update required; ensure any custom dialplans that rely on unauthenticated SUBSCRIBE are reviewed

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

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,600. Get the upgrade done

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Free · runs locally
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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-2021-41157 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
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