CVE-2015-3008 in Asterisk
Summary
by MITRE
Asterisk Open Source 1.8 before 1.8.32.3, 11.x before 11.17.1, 12.x before 12.8.2, and 13.x before 13.3.2 and Certified Asterisk 1.8.28 before 1.8.28-cert5, 11.6 before 11.6-cert11, and 13.1 before 13.1-cert2, when registering a SIP TLS device, does not properly handle a null byte in a domain name in the subject's Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority.
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Analysis
by VulDB Data Team • 05/03/2022
The vulnerability described in CVE-2015-3008 represents a critical security flaw in the Asterisk Open Source telephony platform that affects multiple version lines including 1.8, 11, 12, and 13 series. This issue specifically manifests when SIP TLS devices attempt to register with an Asterisk server, creating a significant attack vector that enables sophisticated man-in-the-middle attacks. The flaw stems from improper handling of null bytes within the Common Name field of X.509 certificates, a fundamental aspect of SSL/TLS certificate validation that should normally prevent such vulnerabilities. The vulnerability is classified under CWE-264, which deals with Permissions, Privileges, and Access Controls, and specifically relates to improper certificate validation mechanisms that allow attackers to bypass security checks through crafted certificates.
The technical implementation of this vulnerability exploits a weakness in how Asterisk processes certificate subject information during the SIP TLS registration process. When a device attempts to register using TLS, the system examines the certificate's Common Name field to verify the server's identity. However, the null byte handling flaw causes the system to truncate or misinterpret the domain name contained within the certificate's CN field, potentially allowing an attacker to present a certificate with a malicious domain name that appears valid to the system. This creates a scenario where an attacker with access to a legitimate Certificate Authority's certificate can craft a malicious certificate that bypasses normal validation procedures, effectively enabling certificate spoofing attacks. The vulnerability is particularly dangerous because it operates at the TLS layer where trust is established, making it a fundamental break in the security model.
The operational impact of CVE-2015-3008 is severe and far-reaching for organizations relying on Asterisk-based telephony systems. Attackers can leverage this vulnerability to intercept, modify, or redirect SIP communications between devices and the Asterisk server, potentially compromising voice communications, authentication mechanisms, and call routing. The attack requires minimal prerequisites since it exploits a weakness in certificate validation rather than requiring complex cryptographic attacks or system compromise. Organizations using affected versions of Asterisk are exposed to unauthorized access to their communication infrastructure, which could lead to eavesdropping, call tampering, or complete system takeover. The vulnerability affects both open source and certified versions of Asterisk, indicating a widespread impact across the telephony ecosystem that relies on these platforms for voice communication services.
Mitigation strategies for this vulnerability center on immediate software updates to patched versions of the Asterisk platform, specifically targeting the version releases mentioned in the CVE description including 1.8.32.3, 11.17.1, 12.8.2, and 13.3.2 for the open source versions, and their corresponding certified releases. System administrators should implement comprehensive certificate validation policies that include additional checks beyond the basic Common Name field, such as Subject Alternative Name validation and proper null byte sanitization. Network segmentation and monitoring should be enhanced to detect unusual registration patterns or certificate validation failures that might indicate exploitation attempts. Organizations should also consider implementing certificate pinning mechanisms where appropriate, though this approach must be carefully balanced against certificate management complexity. The vulnerability aligns with ATT&CK technique T1552.001, which covers credentials in files, and T1046, which involves network service scanning, as attackers would likely attempt to identify vulnerable systems and then exploit the certificate validation weakness to gain unauthorized access to communication channels.