IRONSMITHINTEL
CRITICALCVSS9.8
|
Actively Exploited
|CISA KEV|CVE-2020-3161|Auth: none — unauthenticated|Reboot: required|Manual only

Cisco IP Phones Web Server Remote Code Execution and Denial-of-Service Vulnerability

Cisco IP Phones contain an improper input validation vulnerability for HTTP requests. Exploitation could allow an attacker to execute code remotely with root privileges or cause a denial-of-service (DoS) condition.

Published Apr 15, 2020 · Updated May 16, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

A remote attacker, without authentication, can achieve full data confidentiality loss, arbitrary modification of data, complete denial of service or system unavailability. Federal agencies are required to remediate by 2022-05-03 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Improper Input Validation (CWE-20) vulnerability in Cisco Cisco IP Phones. A vulnerability in the web server for Cisco IP Phones could allow an unauthenticated, remote attacker to execute code with root privileges or cause a reload of an affected IP phone, resulting in a denial of service (DoS) condition. The vulnerability is due to a lack of proper input validation of HTTP requests. An attacker could exploit this vulnerability by sending a crafted HTTP request to the web server of a targeted device. A successful exploit could allow the attacker to remotely execute code with root privileges or cause a reload of an affected IP phone, resulting in a DoS condition. Exploitation requires remote network access, low attack complexity, no authentication required, and no user interaction required.

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Phishing link

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Malicious file

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Server compromised

Am I affected?Quick check

Probably yes if any of these apply:

Network Security Team
Firewall Administrators
IT Security
Running ip phone 8865 firmware: 10.3\(1\)es14, 11.0\(1\), 11.0\(5\)sr1; ip phone 8851 firmware: 10.3\(1\)es14, 11.0\(1\), 11.0\(5\)sr1; ip phone 7841 firmware: 11.0\(1\); ip phone 7821 firmware: 11.0\(1\); ip phone 8811 firmware: 10.3\(1\)es14, 11.0\(1\), 11.0\(5\)sr1; ip phone 8861 firmware: 10.3\(1\)es14, 11.0\(1\), 11.0\(5\)sr1; ip phone 8845 firmware: 10.3\(1\)es14, 11.0\(1\), 11.0\(5\)sr1; ip phone 7861 firmware: 11.0\(1\); ip phone 8841 firmware: 10.3\(1\)es14, 11.0\(1\), 11.0\(5\)sr1; ip phone 7811 firmware: 11.0\(1\); ip phone 8821 firmware: 10.3\(1\)es14, 11.0\(1\), 11.0\(5\)sr1; ip phone 8821-ex firmware: 10.3\(1\)es14, 11.0\(1\), 11.0\(5\)sr1; 8831 firmware: 10.3\(1\)es14, 11.0\(1\), 11.0\(5\)sr1
Real-world incidentsWhat we've seen

Active exploitation documented in the wild. Threat-research write-up: http://packetstormsecurity.com/files/157265/Cisco-IP-Phone-11.7-Denial-Of-Service.html

How to patch

Manual remediation steps

Apply the Vendor Patch

This vulnerability is in the CISA Known Exploited Vulnerabilities catalog — apply the vendor's security update as soon as possible.

CISA required action: Apply updates per vendor instructions.

References

    1
    Vendor advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-voip-phones-rce-dos-rB6EeRXs
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2020-3161
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-3161
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