CVE-2015-6418 in Small Business RV
Summary
by MITRE
The random-number generator on Cisco Small Business RV routers 4.x and SA500 security appliances 2.2.07 does not have sufficient entropy, which makes it easier for remote attackers to determine a TLS key pair via unspecified computations upon handshake key-exchange data, aka Bug ID CSCus15224.
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Analysis
by VulDB Data Team • 07/01/2022
The vulnerability identified as CVE-2015-6418 affects Cisco Small Business RV routers running software version 4.x and SA500 security appliances with firmware version 2.2.07. This weakness resides in the implementation of the random-number generator used during TLS key exchange processes, creating a significant security risk for organizations relying on these devices for network protection. The flaw specifically impacts the cryptographic strength of the TLS handshake mechanism, potentially allowing malicious actors to compromise secure communications.
The technical root cause of this vulnerability stems from insufficient entropy in the random-number generation process employed by the affected Cisco devices. When establishing TLS connections, these appliances use a pseudo-random number generator that lacks adequate randomness properties, making it susceptible to prediction attacks. The vulnerability allows remote attackers to perform unspecified computations on handshake key-exchange data, effectively reducing the complexity of cryptographic key determination. This weakness directly relates to CWE-330, which addresses insufficient entropy in random number generators, and represents a critical flaw in cryptographic implementation that undermines the fundamental security assumptions of TLS encryption protocols.
The operational impact of CVE-2015-6418 extends beyond simple cryptographic weakness to encompass potential complete compromise of secure communications passing through affected networks. Attackers who successfully exploit this vulnerability can potentially decrypt sensitive data transmitted over TLS connections, including authentication credentials, personal information, and business-critical communications. This weakness particularly affects organizations using these devices as network gateways or security appliances, where they serve as primary points of ingress and egress for encrypted traffic. The vulnerability creates a persistent threat vector that can remain active as long as the affected firmware versions persist in operational environments.
Organizations should immediately implement mitigations including firmware updates from Cisco to address the entropy deficiency in the random-number generator. The recommended approach involves upgrading to the latest firmware versions that contain improved cryptographic implementations and sufficient entropy sources. Network administrators should also consider implementing additional security controls such as monitoring for unusual network traffic patterns that might indicate exploitation attempts, and establishing more robust key management practices for TLS connections. The vulnerability demonstrates the critical importance of entropy quality in cryptographic systems and aligns with ATT&CK technique T1552.001, which covers credentials from password storage devices, as compromised TLS keys can lead to credential exposure and further network compromise.