CVE-2007-5469 in OpenSER
Summary
by MITRE
** DISPUTED ** OpenSER 1.2.2 does not verify the Digest authentication header URI against the Request URI in SIP messages, which allows remote attackers to use sniffed Digest authentication credentials to call arbitrary telephone numbers or spoof caller ID (aka "toll fraud and authentication forward attack"). NOTE: Debian disputes this issue, stating that "having the two URIs mismatch is allowed by the standard and happens in some setups for valid reasons."
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Analysis
by VulDB Data Team • 08/08/2024
The vulnerability described in CVE-2007-5469 pertains to a critical security flaw in OpenSER version 1.2.2, a widely used Session Initiation Protocol (SIP) server implementation. This issue represents a significant weakness in the authentication mechanism that governs SIP communications, potentially enabling unauthorized access to telephony services. The vulnerability specifically targets the Digest authentication process, which is fundamental to securing SIP-based voice and video communications. When a SIP client attempts to establish a connection or make a call, it must provide authentication credentials that are verified by the server to ensure legitimate access. The flaw occurs during this verification process, where the system fails to validate that the URI present in the Digest authentication header matches the actual Request URI in the SIP message. This mismatch creates a dangerous gap in the authentication framework that malicious actors can exploit to gain unauthorized access to telephony services.
The technical nature of this vulnerability stems from the failure to implement proper URI validation within the Digest authentication mechanism. According to the Common Weakness Enumeration framework, this issue maps to CWE-287, which addresses improper authentication vulnerabilities. The flaw essentially allows attackers to perform what is known as a "forward attack" or "authentication forward attack" where stolen credentials can be reused against different URIs within the same session. This occurs because the server accepts authentication tokens that were originally generated for one URI but are then applied to another URI within the same SIP transaction. The standard SIP protocol specification allows for certain scenarios where URI mismatches might occur legitimately, particularly in complex network setups involving proxies or load balancers. However, the OpenSER implementation fails to properly distinguish between legitimate and malicious URI mismatches, creating an exploitable condition that undermines the security of the entire authentication system.
The operational impact of this vulnerability extends far beyond simple unauthorized access to SIP services. The most significant consequence involves toll fraud, where attackers can use compromised credentials to make expensive international or long-distance calls without proper authorization. This represents a direct financial threat to organizations using SIP-based telephony systems, as attackers can potentially rack up substantial charges by making calls to premium rate numbers or international destinations. Additionally, the vulnerability enables caller ID spoofing, allowing malicious actors to impersonate legitimate users or organizations within the network. This capability can be leveraged for social engineering attacks, where attackers might masquerade as trusted entities to gain further access to network resources or to manipulate other users. The attack vector is particularly concerning because it requires minimal technical expertise to execute, making it accessible to a broad range of threat actors. The vulnerability essentially undermines the fundamental security assumptions of SIP-based communication systems, potentially compromising the integrity of voice and video services across the entire network infrastructure.
The mitigation strategies for this vulnerability involve multiple layers of security measures that address both the immediate technical flaw and broader system security. Organizations should implement proper URI validation within their SIP servers, ensuring that authentication headers are rigorously checked against the corresponding request URIs before granting access to telephony services. This approach aligns with the principle of least privilege and proper authentication verification as recommended in the ATT&CK framework for network security. The most effective immediate solution involves upgrading to a patched version of OpenSER or migrating to a more secure SIP server implementation that properly validates authentication headers. Network administrators should also implement additional monitoring and logging mechanisms to detect suspicious authentication patterns or unauthorized access attempts. The Debian reference to this issue highlights the complexity of SIP protocol implementations and the need for careful consideration of standard compliance versus security requirements. Organizations must balance the legitimate need for URI flexibility in complex network environments with the imperative to maintain robust authentication security. Regular security audits of SIP implementations and proper configuration management are essential to prevent similar vulnerabilities from emerging in other components of the communication infrastructure.