High priorityDisclosed

Advisory · CVE-2026-101940

NULL pointer flaw in Junos rpd lets a BGP peer crash the daemon with ISO-VPN egress protection

A NULL pointer dereference in the rpd routing daemon of Junos OS and Junos OS Evolved lets an unauthenticated configured BGP peer cause a denial of service via a BGP UPDATE when ISO-VPN and egress-protection configuration is enabled. 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-2026-101940
CWE-476
Action timing
Immediate
ELI5

Explain it like I’m five

A niche VPN feature combination leaves a pointer unset, and a peer update is all it takes to dereference it.

SIMPLIFIED_ATTACK_PATH03 STEPS
  1. 01Trigger input

    An attacker sends the crafted protocol traffic described for CVE-2026-101940.

  2. 02Weakness trips

    The daemon mishandles the input through the null pointer dereference weakness.

  3. 03Impact lands

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

What happened

Juniper disclosed CVE-2026-101940 in its October 2026 security release: a NULL pointer dereference (CWE-476) in rpd. A configured BGP peer can trigger it with a BGP UPDATE when ISO-VPN and egress-protection configuration is enabled, 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 on devices running ISO-VPN with egress protection, following peer updates.
  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

Feature combinations are where daemon crashes hide. Patch the fleet, not just the boxes you remember enabling this on.