CVE-2011-1637 in Skinny Client Control Protocol Software
Summary
by MITRE
Cisco Unified IP Phones 7900 devices (aka TNP phones) with software before 9.2.1 do not properly verify signatures for software images, which allows local users to gain privileges via a crafted image, aka Bug ID CSCtn65962.
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Analysis
by VulDB Data Team • 11/08/2021
The vulnerability identified as CVE-2011-1637 affects Cisco Unified IP Phones 7900 series devices, commonly referred to as TNP phones, where the software versions prior to 9.2.1 contain a critical flaw in their software image verification mechanism. This vulnerability resides in the authentication and integrity verification processes that are supposed to ensure only legitimate and authorized software images are installed on these telephony devices. The flaw specifically manifests in the improper verification of digital signatures that should validate the authenticity and integrity of software updates and installations.
The technical implementation of this vulnerability stems from insufficient cryptographic validation within the device firmware update process. When a local attacker gains access to the device, they can craft a malicious software image that appears to be properly signed and verified by the device's security mechanisms. This allows the attacker to bypass the normal signature verification checks and install unauthorized code with elevated privileges. The vulnerability represents a failure in the cryptographic verification protocol that should prevent unsigned or tampered software from being executed on the device, creating a path for privilege escalation attacks.
From an operational impact perspective, this vulnerability poses significant security risks to organizations relying on Cisco Unified IP Phones for their communication infrastructure. Local attackers who can access the device either physically or through network-based access can exploit this vulnerability to gain elevated privileges and potentially establish persistent backdoors within the network. The implications extend beyond individual device compromise as these phones often serve as critical communication endpoints within enterprise networks, potentially providing attackers with access to internal communication channels and serving as entry points for broader network infiltration. The vulnerability also violates fundamental security principles of integrity verification and access control enforcement.
The mitigation strategies for this vulnerability involve immediate software patching to version 9.2.1 or later, which contains the corrected signature verification mechanisms. Organizations should also implement network segmentation to limit access to these devices and establish strict access controls for administrative functions. Regular security assessments should include verification of device integrity and proper signature validation. This vulnerability aligns with CWE-310, which addresses cryptographic issues, and relates to ATT&CK technique T1068, involving exploit for privilege escalation. Additionally, the weakness demonstrates characteristics of improper verification of cryptographic signatures as outlined in NIST SP 800-57, emphasizing the importance of proper cryptographic implementation in embedded systems and network devices.