CVE-2026-102177: CWE-787 Out-of-bounds Write in Juniper Networks Junos OS

This vulnerability (CVE-2026-102177) involves an out-of-bounds write in the routing protocol daemon (rpd) component of Juniper Networks Junos OS and Junos OS Evolved. An adjacent unauthenticated attacker can exploit this flaw when IS-IS link protection and backup-selection features are configured, leading to a denial of service condition. The vulnerability has a CVSS 3.1 base score of 7.6, indicating high severity with network attack vector requiring no privileges or user interaction. Multiple version ranges of Junos OS and Junos OS Evolved are affected, as explicitly enumerated in the affectedVersions field.

Successful exploitation allows an adjacent unauthenticated attacker to cause a denial of service on affected devices running Junos OS or Junos OS Evolved with IS-IS link protection and backup-selection configured. The impact includes loss of availability of routing services, potentially disrupting network operations. There is also limited confidentiality and integrity impact as per the CVSS vector.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official patch or fix links were provided in the input data. Users should monitor Juniper Networks advisories for updates and apply patches or mitigations once available. Until then, consider disabling IS-IS link protection and backup-selection if feasible to reduce exposure.