CVE-2015-2924 in NetworkManager
Summary
by MITRE
The receive_ra function in rdisc/nm-lndp-rdisc.c in the Neighbor Discovery (ND) protocol implementation in the IPv6 stack in NetworkManager 1.x allows remote attackers to reconfigure a hop-limit setting via a small hop_limit value in a Router Advertisement (RA) message, a similar issue to CVE-2015-2922.
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Analysis
by VulDB Data Team • 04/11/2018
The vulnerability described in CVE-2015-2924 represents a critical flaw in NetworkManager's implementation of the IPv6 Neighbor Discovery protocol, specifically within the receive_ra function located in rdisc/nm-lndp-rdisc.c. This issue affects NetworkManager versions 1.x and enables remote attackers to manipulate hop-limit settings through maliciously crafted Router Advertisement messages. The vulnerability operates by exploiting the lack of proper validation for hop_limit values in RA messages, allowing attackers to inject small hop_limit values that can alter network configuration parameters. The flaw essentially permits unauthorized modification of network routing behavior through manipulation of IPv6 neighbor discovery mechanisms, creating a significant security risk for systems relying on NetworkManager for network configuration management.
The technical implementation of this vulnerability stems from insufficient input validation within the neighbor discovery protocol handling code. When NetworkManager processes Router Advertisement messages, it fails to properly validate the hop_limit field, which should typically be set to 1 for router advertisements according to RFC 4862. Attackers can craft RA messages with deliberately small hop_limit values that bypass normal validation checks, allowing them to override the system's hop-limit configuration. This specific flaw falls under CWE-20, which describes improper input validation, and demonstrates how inadequate parameter checking in network protocol implementations can lead to configuration manipulation. The vulnerability operates at the network stack level, directly affecting how IPv6 neighbor discovery messages are processed and interpreted by the NetworkManager daemon.
The operational impact of CVE-2015-2924 extends beyond simple configuration changes, as it can enable attackers to manipulate network routing behavior and potentially facilitate more sophisticated attacks. When an attacker successfully exploits this vulnerability, they can alter hop-limit values that affect how packets are forwarded through the network, potentially causing routing loops, packet loss, or enabling man-in-the-middle attacks. The vulnerability is particularly dangerous in environments where NetworkManager automatically processes RA messages without proper validation, as it can silently modify network behavior without administrator awareness. This type of attack aligns with ATT&CK technique T1071.004, which involves application layer protocol manipulation, and represents a form of network configuration poisoning that can persist across system reboots if not properly addressed.
Mitigation strategies for CVE-2015-2924 require both immediate patching and configuration hardening measures. Organizations should immediately update NetworkManager to versions that contain fixes for this vulnerability, typically those released after the vulnerability disclosure in 2015. System administrators should also implement proper network segmentation and monitoring to detect unusual RA message patterns that might indicate exploitation attempts. Additional defensive measures include disabling automatic RA processing when not required, implementing network access controls to limit which hosts can send RA messages, and configuring firewalls to filter out RA messages from untrusted sources. The vulnerability demonstrates the importance of validating all network protocol parameters and implementing proper input sanitization in network management software, particularly in components that handle neighbor discovery protocols where configuration changes can have widespread network impact. Organizations should also consider implementing network monitoring solutions that can detect anomalous hop-limit values in RA messages as part of their overall network security posture.