CVE-2021-41157

Home/CVE/FreeSWITCH is a Software Defined Telecom Stack enabling the digital transformation from proprietary telecom switches to

CVE

FreeSWITCH is a Software Defined Telecom Stack enabling the digital transformation from proprietary telecom switches to

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.

MEDIUM · CVSS 5.3 EPSS 0.00465

Schedule remediation

Public exploit or PoC is available

Sigma rules0 YARA rules0

Look this up elsewhere - one-click external pivots

NVD CVE.org CISA Vulners Exploit-DB GitHub PoC VulnCheck KEV GreyNoise

▸ How to read a CVE - triage first, then detect and patch

This page is every public fact about CVE-2021-41157, cross-linked. Its job is to answer one question fast - does this need my attention now? - and then hand you the two things you do about it. Here is how an analyst reads it.

Triage: should I act now? Four signals, and they are not interchangeable:

CVSSseverity - how bad it is IF exploited, 0-10. A high CVSS alone is not urgency; a flaw can be a perfect 10 and never actually be attacked. EPSSprobability - a model’s estimate of the chance it is exploited in the next 30 days, 0-1. This is the “will it actually happen” signal. CISA KEVconfirmed - it is being exploited in the wild right now. The strongest signal on the page; KEV beats any score. Weaponisedavailability - public exploits / PoCs, and especially Metasploit modules rated Excellent / Great. Reliable, packaged exploit code means low-skill attackers can use it today.

How they combine: KEV, or a dependable Metasploit module, means patch now regardless of CVSS. High CVSS + low EPSS + no exploit is real but not an emergency - schedule it. Low CVSS but KEV-listed still gets patched now. The verdict above already weighed these for you; this is how it got there.

Then what - two workflows:

Detectwhen you cannot patch today, follow this CVE to the ATT&CK techniques it enables, then Build a SIEM detection (the green button) - author a rule, test it in Atomic, deploy it. That buys visibility while the patch waits. PatchAffected products / packages tell you if you are exposed; Fixed versions by distribution and Vendor advisories give the exact version that closes it.

Reading order for the panels below: verdict + badges, then Public exploits / Metasploit (is it weaponised), then ATT&CK techniques + Sigma / IDS rules (can I detect it), then Affected products / packages + Fixed versions (am I exposed, what patches it), then Threat actors / IOCs (who uses it), then Scoring & timeline / references (the evidence).

View attack path from CVE-2021-41157

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ATT&CK techniques

Techniques this CVE enables - linked via CWECAPECATT&CK. High◆ = named directly in ATT&CK or Nuclei templates.

T1040 · Network Sniffing T1134 · Access Token Manipulation T1185 · Browser Session Hijacking T1505.003 · Web Shell T1548 · Abuse Elevation Control Mechanism T1550.001 · Application Access Token T1557 · Adversary-in-the-Middle T1563 · Remote Service Session Hijacking

▤ Build a SIEM detection for these techniques

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CAPEC attack patterns

Attack patterns this CVE enables - the bridge from weakness to ATT&CK technique.

CAPEC-CAPEC-114 · Authentication Abuse CAPEC-CAPEC-115 · Authentication Bypass CAPEC-CAPEC-12 · Choosing Message Identifier CAPEC-CAPEC-151 · Identity Spoofing CAPEC-CAPEC-166 · Force the System to Reset Values CAPEC-CAPEC-194 · Fake the Source of Data CAPEC-CAPEC-216 · Communication Channel Manipulation CAPEC-CAPEC-22 · Exploiting Trust in Client CAPEC-CAPEC-36 · Using Unpublished Interfaces or Functionality CAPEC-CAPEC-57 · Utilizing REST's Trust in the System Resource to Obtain Sensitive Data CAPEC-CAPEC-593 · Session Hijacking CAPEC-CAPEC-62 · Cross Site Request Forgery

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Weakness Classification

CWE-287Improper Authentication

CWE-306Missing Authentication for Critical Function

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Affected Products & Versions

freeswitch< 1.10.6

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Public Exploits & PoCs

These PoC and exploit links come from public sources and are not verified to be safe or functional. Review the code before running anything, and treat unverified entries as untrusted.
pocPublic PoC (nvd-reference)
poc0xInfection/PewSWITCH (trickest)
pocARPSyndicate/cvemon (trickest)
pocEnableSecurity/awesome-rtc-hacking (trickest)
poctaielab/awesome-hacking-lists (trickest)
pocgithub.com · GHSA-g7xg-7c54-rmpjgithub.com

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Fixed versions by distribution

The package version that resolves this CVE on each Linux distribution, from the vendor’s published security data. fixed in shows a patched version exists; open means the package is listed as affected with no fix yet.

alpine edgefreeswitch fixed in 1.10.7-r0

alpine v3.19freeswitch fixed in 1.10.7-r0

alpine v3.20freeswitch fixed in 1.10.7-r0

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Scoring & Timeline

5.3

MEDIUM · CVSS v3.1 · [email protected]

View on NVD

Attack Vector

Network Adjacent Local Physical

Attack Complexity

Low High

Privileges Required

None Low High

User Interaction

None Required

Scope

Unchanged Changed

Confidentiality

None Low High

Integrity

None Low High

Availability

None Low High

Published to NVD26 Oct 2021 · 02:15 PM

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

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References & Sources

Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.

http://seclists.org/fulldisclosure/2021/Oct/41Mailing ListThird Party Advisory

https://github.com/signalwire/freeswitch/commit/b21dd4e7f3a6f1d5f7be3ea500a319a5bc11db9ePatchThird Party Advisory

https://github.com/signalwire/freeswitch/releases/tag/v1.10.6Release NotesThird Party Advisory