CVE-2026-102178: CWE-121 Stack-based Buffer Overflow in Juniper Networks Junos OS

This vulnerability (CVE-2026-102178) is a stack-based buffer overflow in the BGP routing daemon component of Juniper Networks Junos OS and Junos OS Evolved. It can be triggered by a configured BGP flowspec peer through flowspec route re-advertisement when BGP update-threading is enabled. Successful exploitation may lead to routing-engine compromise or denial of service of the routing daemon. The vulnerability affects multiple versions across Junos OS and Junos OS Evolved, including specific release ranges prior to 23.2R2-S7.7, 23.4R2-S8.13, 24.2R2-S5.5, 24.4R2-S5, 25.2R2-S2, 25.4R1-S3, 26.2R1-S2 and their EVO variants. The CVSS v3.1 base score is 9.8, reflecting network attack vector, low attack complexity, no privileges required, no user interaction, and high impact on confidentiality, integrity, and availability.

An attacker with a configured BGP flowspec peer can exploit this vulnerability to cause a stack-based buffer overflow, potentially leading to compromise of the routing engine or denial of service of the routing daemon. This impacts the confidentiality, integrity, and availability of the affected Junos OS devices. The vulnerability is critical due to the high CVSS score of 9.8 and the potential for complete control or disruption of routing functions.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official patch or workaround information is provided in the available data. Until a fix is available, it is recommended to review BGP flowspec peer configurations and consider disabling BGP update-threading if feasible to reduce exposure. Monitor Juniper Networks advisories for updates and apply patches promptly once released.