Juniper Junos OS CVE-2026-102018

Exploitation requires that the target Junos OS / Junos OS Evolved device be configured for PIM Bidirectional (Bidir) multicast - a non-default protocol feature; devices not running PIM Bidir are not affected. The attacker must occupy an ADJACENT network position (AV:A): directly connected L2 segment or a multicast/routing peer able to deliver a PIM Bidir message to the rpd process - it is not remotely exploitable across arbitrary routed networks. No authentication is required (PR:N) and no user interaction is needed (UI:N). Impact is limited to denial of service (routing daemon crash); there is no code execution, data disclosure, or integrity impact. The adjacency requirement and the PIM Bidir configuration dependency are the primary limiting factors for defenders assessing exposure.

This is a moderate-priority availability issue, not a top-tier emergency. The vendor-supplied CVSS 4.0 vector (AV:A/AC:L/AT:N/PR:N/UI:N) scores 7.1 and indicates an unauthenticated, low-complexity attack requiring only adjacent (directly connected / same broadcast segment) network position, with impact limited strictly to availability (VA:H; VC:N/VI:N - no confidentiality or integrity loss). The adjacent attack vector is a meaningful real-world limiter: an attacker must already have a foothold on a connected network segment or peer with the device, which sharply reduces the exposed population versus a fully routable (AV:N) flaw. No EPSS score, CISA KEV listing, POC, or SSVC decision data was provided in the input, so exploitation probability cannot be quantified; based on signals available this is 'no public exploit identified at time of analysis.' Exploitation also depends on PIM Bidirectional multicast being configured, a non-default feature, further narrowing realistic risk. Net: a legitimate crash/DoS concern for operators running PIM Bidir on Junos, but the adjacency requirement and config dependency make it a patch-on-normal-cycle item rather than a drop-everything priority, absent any evidence of active exploitation.

An attacker positioned on a network segment directly adjacent to a Junos OS or Junos OS Evolved device (e.g., a compromised peer router or a host on the same L2 segment participating in multicast) crafts and sends a malformed PIM Bidirectional message to the target. The message triggers a NULL pointer dereference in the routing protocol daemon (rpd), crashing it and causing a denial-of-service/routing outage. No public exploit code was identified in the provided data, and exploitation requires PIM Bidir to be configured on the target.