CVE-2026-102027 in Junos OS
Summary
by MITRE • 10/14/2026
An Incorrect Calculation of Buffer Size vulnerability in the routing protocol daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows a configured eBGP neighbor to cause an rpd crash via BGP labeled-unicast UPDATEs when the affected multipath features are enabled.
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Analysis
by VulDB Data Team • 10/14/2026
The identified vulnerability resides within the routing protocol daemon, known as rpd, of Juniper Networks Junos Operating System and Junos OS Evolved platforms. This flaw is classified under CWE-190, which denotes an Integer Overflow or Wraparound leading to incorrect buffer size calculations. The specific trigger mechanism involves a configured external Border Gateway Protocol (eBGP) neighbor sending BGP labeled-unicast UPDATE messages that exploit the miscalculation logic within the daemon's processing routines. This issue is not universally present but requires specific conditions, namely that certain multipath features are enabled on the affected device. When these conditions align and malicious or malformed traffic is received from a configured eBGP peer, the incorrect calculation results in memory allocation errors that ultimately cause the rpd process to crash.
From an operational perspective, the consequence of this vulnerability is significant due to its direct impact on network stability and availability. The crashing of the routing protocol daemon disrupts the device's ability to maintain routing tables and exchange route information with peers. This leads to a loss of connectivity for traffic relying on those routes and can cause broader network instability if multiple devices are affected or if critical infrastructure relies heavily on BGP sessions that become unstable due to repeated crashes. The attack vector is remote, requiring only network access to the targeted device's management plane or data plane where eBGP peering occurs. This aligns with MITRE ATT&CK technique T1498, Network Denial of Service, specifically through resource exhaustion via protocol exploitation. An attacker could potentially use this flaw in a denial-of-service campaign by repeatedly sending crafted labeled-unicast UPDATE messages to force continuous daemon restarts, thereby degrading network performance and reliability without needing authentication credentials if the BGP session is already established or can be initiated.
Mitigation strategies must focus on both immediate remediation and long-term architectural hardening. The primary defense is applying the vendor-provided software patches that address the integer overflow logic within the rpd component of Junos OS and Junos OS Evolved. Organizations should prioritize updating systems where eBGP multipath features are enabled, as these configurations present the highest risk surface. In addition to patching, network segmentation and access control lists can be employed to restrict which peers are allowed to establish BGP sessions with vulnerable devices, thereby limiting exposure to untrusted networks. Monitoring tools should also be configured to detect abnormal patterns in BGP UPDATE traffic or frequent daemon restarts, serving as an early warning system for potential exploitation attempts before significant service disruption occurs.