CVE-2017-15865 in FRRouting
Summary
by MITRE
bgpd in FRRouting (FRR) before 2.0.2 and 3.x before 3.0.2, as used in Cumulus Linux before 3.4.3 and other products, allows remote attackers to obtain sensitive information via a malformed BGP UPDATE packet from a connected peer, which triggers transmission of up to a few thousand unintended bytes because of a mishandled attribute length, aka RN-690 (CM-18492).
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Analysis
by VulDB Data Team • 01/23/2021
The vulnerability identified as CVE-2017-15865 represents a critical information disclosure flaw within the bgpd component of FRRouting software, affecting versions prior to 2.0.2 and 3.x prior to 3.0.2. This issue specifically impacts Cumulus Linux versions before 3.4.3 and other products utilizing FRRouting, creating a significant security risk for network infrastructure deployments. The vulnerability manifests when a malicious or compromised BGP peer sends a malformed UPDATE packet to a vulnerable system, triggering unintended data exposure through improper handling of attribute length fields. This flaw operates at the border gateway protocol level where network routing decisions are made, making it particularly dangerous for enterprise and service provider networks that rely heavily on BGP for inter-domain routing.
The technical root cause of this vulnerability stems from a buffer handling error in the bgpd daemon's processing of BGP attributes, specifically related to how the system calculates and validates attribute lengths within UPDATE messages. When a malformed packet is received, the system fails to properly validate the attribute length field, leading to a situation where the parser attempts to read beyond the intended buffer boundaries. This mismanagement results in the accidental transmission of several thousand unintended bytes from memory locations adjacent to the parsed data structures. The vulnerability is classified as a buffer over-read condition that can be exploited remotely without authentication, as the malicious packet can be sent from any connected BGP peer. This issue directly maps to CWE-125: Out-of-bounds Read, which is categorized under the broader weakness of improper input validation in network protocol implementations.
The operational impact of CVE-2017-15865 extends beyond simple information disclosure, as the unintended data transmission may contain sensitive system information including routing table contents, peer configurations, authentication credentials, or other confidential data that could be leveraged by attackers for further exploitation. Network administrators face the risk of exposing internal routing information that could aid in mapping network topology, identifying vulnerable systems, or facilitating more sophisticated attacks such as route injection or prefix hijacking. The vulnerability can be exploited by any connected BGP peer, including malicious actors who may have gained access to a legitimate peer connection through various attack vectors. This makes the impact particularly severe in environments where BGP peers are not properly secured or where network segmentation is inadequate, as the attack surface expands to include all connected routing peers. The issue also aligns with ATT&CK technique T1071.004: Application Layer Protocol, specifically targeting BGP protocol communications.
Mitigation strategies for this vulnerability require immediate patching of affected FRRouting installations to versions 2.0.2 or 3.0.2 and later, with affected Cumulus Linux deployments needing updates to version 3.4.3 or higher. Network administrators should implement additional defensive measures including BGP peer authentication using MD5 signatures, implementing proper access control lists to restrict BGP peer connections, and monitoring for unusual BGP UPDATE packet patterns that may indicate exploitation attempts. The vulnerability can also be addressed through network segmentation to limit BGP peer connectivity, implementing BGP route filtering to prevent malicious route announcements, and establishing robust network monitoring to detect abnormal data transmission patterns. Organizations should also conduct comprehensive vulnerability assessments to identify all systems running affected versions of FRRouting and ensure proper patch management procedures are in place to prevent similar issues in the future. This vulnerability demonstrates the critical importance of proper input validation in network protocol implementations and highlights the need for continuous security auditing of core networking components that operate with minimal user interaction and maximum system privilege levels.