CVE-2017-3865 in StarOS
Summary
by MITRE
A vulnerability in the IPsec component of Cisco StarOS for Cisco ASR 5000 Series Routers could allow an unauthenticated, remote attacker to terminate all active IPsec VPN tunnels and prevent new tunnels from establishing, resulting in a denial of service (DoS) condition. Affected Products: ASR 5000 Series Routers, Virtualized Packet Core (VPC) Software. More Information: CSCvc21129. Known Affected Releases: 21.1.0 21.1.M0.65601 21.1.v0. Known Fixed Releases: 21.2.A0.65754 21.1.b0.66164 21.1.V0.66014 21.1.R0.65759 21.1.M0.65749 21.1.0.66030 21.1.0.
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Analysis
by VulDB Data Team • 12/30/2020
The vulnerability described in CVE-2017-3865 represents a critical denial of service weakness within the IPsec implementation of Cisco StarOS software running on ASR 5000 Series Routers and Virtualized Packet Core environments. This flaw resides in the secure communication protocols that govern IPsec VPN tunnel establishment and maintenance, creating an avenue for remote exploitation without requiring authentication credentials. The attack vector specifically targets the IPsec component's handling of tunnel termination and establishment processes, allowing malicious actors to disrupt network connectivity for legitimate users.
The technical mechanism behind this vulnerability involves improper state management and validation within the IPsec processing pipeline of the affected Cisco products. When an unauthenticated remote attacker exploits this weakness, they can manipulate the IPsec tunnel management functions to forcibly terminate existing active tunnels while simultaneously blocking the creation of new connections. This creates a cascading failure effect where network security infrastructure becomes compromised, leading to complete disruption of IPsec-based communications. The flaw essentially allows an attacker to perform a coordinated denial of service attack against the router's security services, affecting all users relying on IPsec VPN connectivity.
From an operational impact perspective, this vulnerability poses significant risks to organizations dependent on secure remote access and network connectivity through IPsec tunnels. The affected ASR 5000 Series Routers serve as critical infrastructure components in telecommunications environments, making the potential for widespread service disruption particularly concerning. Network administrators face the challenge of maintaining secure communications while dealing with the possibility of unauthorized termination of security sessions, potentially exposing sensitive data flows to interception or disruption. The vulnerability affects both hardware and virtualized deployments, amplifying its potential impact across different network architectures and deployment models.
The mitigation strategy for this vulnerability requires immediate implementation of software updates and patches provided by Cisco, specifically targeting the releases mentioned in the advisory. Organizations should prioritize updating their ASR 5000 Series Routers and VPC Software installations to versions 21.2.A0.65754, 21.1.b0.66164, and other fixed releases to eliminate the risk of exploitation. Network security teams should also implement monitoring solutions to detect anomalous IPsec tunnel behavior that might indicate exploitation attempts. Additionally, temporary network segmentation and access control measures can provide additional protection layers while permanent patches are deployed. This vulnerability aligns with CWE-209, which addresses improper handling of exceptions, and maps to ATT&CK technique T1499.004 for network denial of service attacks, highlighting the need for comprehensive defensive measures including intrusion detection systems and proper network access controls to prevent unauthorized exploitation of such security weaknesses in enterprise and telecommunications environments.