CVE-2023-40457 in ExtremeXOS
Summary
by MITRE • 11/11/2024
The BGP daemon in Extreme Networks ExtremeXOS (aka EXOS) 30.7.1.1 allows an attacker (who is not on a directly connected network) to cause a denial of service (BGP session reset) because of BGP attribute error mishandling (for attribute 21 and 25). NOTE: the vendor disputes this because it is "evaluating support for RFC 7606 as a future feature" and believes that "customers that have chosen to not require or implement RFC 7606 have done so willingly and with knowledge of what is needed to defend against these types of attacks."
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Analysis
by VulDB Data Team • 11/11/2024
The vulnerability described in CVE-2023-40457 affects the Border Gateway Protocol daemon within Extreme Networks ExtremeXOS operating system version 30.7.1.1, representing a significant denial of service risk for network infrastructure. This issue stems from improper handling of BGP attribute errors, specifically concerning attributes 21 and 25, which are critical components in BGP message processing and route advertisement. The flaw enables remote attackers who are not directly connected to the network to trigger BGP session resets, effectively disrupting routing operations and potentially causing widespread network connectivity issues. This vulnerability operates at the core of internet routing protocols where BGP serves as the primary protocol for exchanging routing information between autonomous systems, making it a critical target for network attackers seeking to cause disruption.
The technical implementation of this vulnerability demonstrates a classic flaw in protocol error handling mechanisms where the BGP daemon fails to properly process malformed or unexpected BGP attributes. Attribute 21 typically corresponds to the ORIGIN attribute while attribute 25 relates to the MP_REACH_NLRI attribute, both of which are fundamental to BGP route validation and advertisement processes. When these attributes are improperly handled, the system experiences a cascade of errors that ultimately results in session termination rather than graceful error recovery or message filtering. This represents a violation of proper error handling principles as outlined in CWE-248, which addresses "Uncaught Exception" conditions in software implementations, and directly relates to the BGP protocol's specification requirements for robust error management. The improper error handling creates a condition where legitimate network operations can be disrupted by maliciously crafted BGP messages, essentially allowing for a form of protocol-based denial of service attack.
The operational impact of this vulnerability extends beyond simple service disruption, as it can potentially compromise the stability and reliability of entire network infrastructures that rely on BGP for routing decisions. When BGP sessions reset due to attribute errors, network devices must re-establish connections and re-synchronize routing information, which can result in temporary routing black holes, increased convergence times, and potential service degradation for end users. The vulnerability is particularly concerning because it affects remote attackers who do not require physical or direct network access, making it an attractive target for cybercriminals seeking to disrupt network operations without requiring sophisticated access methods. According to MITRE ATT&CK framework, this vulnerability maps to T1499.004 which covers "Endpoint Denial of Service" and represents a network-level attack vector that can be classified as a protocol-based attack. The attack surface is broad as any network node running the affected ExtremeXOS version could be targeted, potentially affecting transit providers, internet exchange points, and enterprise network infrastructure that depends on BGP for routing.
The vendor response to this vulnerability reflects a complex relationship between security implementation and industry standard adoption, as Extreme Networks has disputed the classification of this issue while acknowledging ongoing evaluation of RFC 7606 support. This stance highlights the gap between existing security practices and recommended protocol enhancements, where RFC 7606 specifically addresses "The BGP Attribute Error Handling" and provides guidelines for more robust error handling in BGP implementations. The vendor's position suggests that customers who have not implemented RFC 7606 are doing so at their own risk, which creates a dangerous precedent where network administrators may be left without adequate protection against known vulnerabilities. This response aligns with the broader cybersecurity challenge of balancing backward compatibility with security improvements, and represents a gap in the security posture where organizations must either implement additional mitigations or accept the risk of potential service disruption. Organizations should consider implementing network segmentation, BGP route filtering, and monitoring mechanisms to detect and prevent exploitation of this vulnerability until proper vendor patches are available. Additionally, implementing BGP security measures such as BGPsec or Route Origin Authorization can provide additional protection layers against similar attribute-based attacks that exploit protocol implementation weaknesses.