High priorityDisclosed

Advisory · CVE-2026-101942

Length handling flaw in Junos rpd lets an EVPN peer crash the daemon on re-advertisement

An improper handling of length parameter inconsistency vulnerability in the routing protocol daemon (rpd) of Junos OS and Junos OS Evolved lets an unauthenticated network attacker cause a denial of service via a malformed EVPN Type-3 or Type-4 route received from a configured EVPN peer and processed during re-advertisement. Juniper rates it CVSS 4.0 8.7 (CVSS 3.1 7.5).

Advisory published October 14, 2026Independent summary
Vendor
Juniper Networks
Product
Junos OS
Identifier / CWE
CVE-2026-101942
CWE-130
Action timing
Immediate
ELI5

Explain it like I’m five

Two parts of the daemon disagree about how long an EVPN route is, and the disagreement crashes the daemon when the route is passed along.

SIMPLIFIED_ATTACK_PATH03 STEPS
  1. 01Trigger input

    An attacker sends the crafted protocol traffic described for CVE-2026-101942.

  2. 02Weakness trips

    The daemon mishandles the input through the improper handling of length parameter inconsistency weakness.

  3. 03Impact lands

    The routing or control-plane daemon crashes or misbehaves as described.

What happened

Juniper disclosed CVE-2026-101942 in its October 2026 security release: an improper handling of length parameter inconsistency (CWE-130) in rpd. A malformed EVPN Type-3 or Type-4 route from a configured EVPN peer triggers it during re-advertisement, denying service.

Juniper’s JSA112187 lists the affected service releases and the October 2026 service release thresholds that carry the fix. Match your exact release to the advisory rather than guessing here.

What to do

  1. Inventory every Junos OS deployment, including test, training, and individually managed instances.
  2. Apply the vendor fix or upgrade exactly as directed in the linked vendor bulletin or advisory.
  3. Restrict network access to Junos OS while remediation is underway, especially for internet-facing instances.
  4. Review application and server logs for rpd crashes during EVPN route re-advertisement, especially Type-3 and Type-4 routes.
  5. Check for accounts, content, or configuration created outside normal change processes, and rotate exposed credentials where access cannot be ruled out.
  6. Verify the deployed version or patch level after remediation.

Management note

Re-advertisement paths get less testing than ingress paths. Patch EVPN fabrics as one change.