CVE-2021-26906 Explained : Impact and Mitigation
Discover the impact of CVE-2021-26906, a vulnerability in Digium Asterisk versions prior to 18.2.0. Learn about the technical details, affected systems, exploitation mechanism, and mitigation steps.
An SDP negotiation vulnerability in the PJSIP in Digium Asterisk versions prior to 18.2.0 can lead to a remote server crashing Asterisk due to a specific SIP response, creating an SDP negotiation failure.
Understanding CVE-2021-26906
This vulnerability affects various versions of Digium Asterisk, potentially allowing a remote attacker to crash the system by manipulating SIP responses.
What is CVE-2021-26906?
CVE-2021-26906 is a security flaw in Digium Asterisk that exists in the PJSIP module, enabling a remote server to cause a denial of service by triggering a specific SDP negotiation failure through crafted SIP responses.
The Impact of CVE-2021-26906
The vulnerability can be exploited remotely by an attacker to crash the Asterisk server, disrupting communication services and potentially leading to system unavailability.
Technical Details of CVE-2021-26906
This section outlines the specific technical information related to the CVE.
Vulnerability Description
The vulnerability resides in the SDP negotiation functionality of PJSIP, allowing an adversary to exploit it by sending malicious SIP responses that trigger a negotiation failure, consequently crashing the Asterisk server.
Affected Systems and Versions
Digium Asterisk versions up to 18.2.0 are affected by this vulnerability, including 13.x, 14.x, 15.x, 16.x, 17.x, and Certified Asterisk versions through 16.8-cert5.
Exploitation Mechanism
Remote attackers can exploit this vulnerability by sending carefully crafted SIP responses to the targeted Asterisk server, leading to a crash and potential denial of service.
Mitigation and Prevention
To safeguard systems from CVE-2021-26906, immediate actions and long-term security measures are necessary.
Immediate Steps to Take
Update Digium Asterisk to version 18.2.0 or apply patches provided by the vendor to mitigate the vulnerability and prevent potential exploitation.
Long-Term Security Practices
Implement network security measures, monitor SIP traffic for anomalies, and maintain awareness of security advisories to protect systems from similar vulnerabilities.
Patching and Updates
Regularly apply security patches and updates released by Digium to ensure the system is protected against known vulnerabilities and exploits.