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Juniper Junos OS CVE-2026-101952

| EUVDEUVD-2026-101493 HIGH
2026-10-14 juniper GHSA-mjrv-f2hg-pqg8
8.7
CVSS 4.0 · Vendor: juniper
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Abuse configured BGP ISO-VPN peering session
  2. Delivery
    Send crafted inconsistent ISO-VPN update
  3. Exploit
    BMP/NSR processes malformed route data
  4. Execution
    rpd validation fails and daemon crashes
  5. Impact
    Routing disrupted (denial of service)

Vulnerability Assessment

Exploitation Conditions

Exploitation requires that (1) the target Junos OS or Junos OS Evolved device is explicitly configured with a BGP ISO-VPN (CLNS/IS-IS L3VPN) peering session with the attacker-controlled peer, and (2) that the crafted ISO-VPN update is processed by either BMP (BGP Monitoring Protocol) route monitoring or NSR (Nonstop Active Routing). Devices without ISO-VPN configured, or with ISO-VPN but neither BMP route monitoring nor NSR enabled, are not exposed. The key limiting factor is the required pre-established peering trust relationship - the attacker must be an accepted BGP ISO-VPN neighbor - which narrows realistic exploitation to compromised or malicious peers rather than arbitrary internet hosts, even though no device-level authentication (PR) is involved.

Impact

This is a genuine high-severity availability risk but with meaningful exploitation gating. The vendor CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N) with VA:H and SA:L yields 8.7, driven entirely by availability impact - there is no confidentiality or integrity exposure (VC:N/VI:N). The score's PR:N is technically accurate for device authentication, but the description makes clear the attacker must already be a CONFIGURED BGP ISO-VPN peer, i.e. the victim device must be deliberately configured to peer with the attacker, which is a substantial trust precondition not reflected in the raw vector - verify against your actual peering topology before treating this as internet-wide unauthenticated. No EPSS score, KEV listing, or POC was provided in the input, so there is no public exploitation signal: no public exploit identified at time of analysis. The practical priority is moderate-to-high for service providers running ISO-VPN (CLNS/IS-IS VPN) with BMP route monitoring or NSR enabled, and low for the large majority of Junos deployments that do not use ISO-VPN. Net: a real crash bug worth patching on exposed route reflectors/PE routers, but not a drop-everything internet-facing issue given the required peering and feature configuration.

Exploit ScenarioDerived

An attacker who controls a device that the target Junos/Junos OS Evolved router is configured to peer with over BGP ISO-VPN sends a specially crafted ISO-VPN update. When the router's rpd processes that update through BMP route monitoring or Nonstop Active Routing (NSR), an input-consistency validation flaw causes rpd to crash, disrupting routing. No public exploit code was identified in the provided data.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.4% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 14, 2026

Denial of service in Juniper Networks Junos OS and Junos OS Evolved: a malformed BGP ISO-VPN (CLNS/IS-IS L3VPN) update from an accepted ISO-VPN peer crashes the routing protocol daemon (rpd) when that update is subsequently handled by BMP route monitoring or by NSR replication, taking down routing on the affected device (CVSS 4.0 base 8.7; AV:N/AC:L/AT:N/PR:N/UI:N with VA:H and SA:L). Exploitation requires no credentials on the wire, but it is gated by a pre-established BGP ISO-VPN peering relationship, so realistic exposure is limited to compromised or malicious peers rather than arbitrary internet hosts, and the device must additionally have BMP route monitoring or NSR enabled. No public exploit code has been identified at time of analysis and the issue is not reported as actively exploited; exploitation yields only availability impact, with no confidentiality or integrity loss on the router itself.

RemediationAI

The source data does not include a fixed version number, so patch availability cannot be independently confirmed here - consult Juniper advisory JSA112187 (https://supportportal.juniper.net/JSA112187) for the exact Junos OS and Junos OS Evolved releases that correct the rpd ISO-VPN consistency check, and upgrade to the prescribed maintenance release on the affected train; since the underlying defect is in how rpd consumes ISO-VPN updates, no configuration change can fully substitute for that fix. Until the patched release is deployed, prioritize compensating controls that shrink the reachable attack surface. First, disable ISO-VPN (remove the BGP ISO-VPN family/peering configuration) if IS-IS L3VPN reachability over BGP is not operationally required - the trade-off is loss of that service, but it eliminates the vulnerable code path entirely. Second, if ISO-VPN must remain, remove the downstream replication trigger: turn off BMP route monitoring for the relevant BGP sessions, or disable NSR (nonstop-routing) on the routing engine - either step prevents the inconsistent update from reaching the crashing path, at the cost of losing route-monitoring visibility to collectors or losing hitless RE failover/redundancy respectively. Third, harden the peer population, since the attacker must already be an accepted ISO-VPN neighbor: restrict ISO-VPN peering to explicitly trusted peers, apply import policy that filters ISO-VPN NLRIs from untrusted neighbors, and enable BGP TCP-MD5/TCP-AO and generalized TTL security (GTSM) to make session hijacking by an off-path attacker harder - these do nothing against a genuinely malicious or already-compromised peer. Finally, monitor for rpd core dumps and unexpected routing-engine failovers as a detection signal, and treat any rpd restart on a device running ISO-VPN with BMP or NSR as a potential exploitation attempt.

Affected VersionsENISA

Junos OS Evolved 23.4 <23.4R2-S8.11-EVO
Junos OS 0 <23.2R2-S7.7
Junos OS 24.2 <24.2R2-S5.5
Junos OS Evolved 26.2 <26.2R1-S2-EVO
Junos OS Evolved 23.4X100
Junos OS Evolved 24.2 <24.2R2-S5.6-EVO
Junos OS 26.2 <26.2R1-S2
Junos OS 23.4 <23.4R2-S8.13
Junos OS Evolved 25.4 <25.4R1-S3-EVO
Junos OS 25.4 <25.4R1-S3
Junos OS 25.2 <25.2R2-S2
Junos OS Evolved 25.2X100 <25.2X100-D35-EVO
Junos OS 24.4 <24.4R2-S5
Junos OS Evolved 25.2 <25.2R2-S2-EVO
Junos OS Evolved 24.4 <24.4R2-S5-EVO
Junos OS Evolved 0 <23.2R2-S7.7-EVO
Junos OS Evolved 25.4X300 <25.4X300-D40-EVO

Affected Packages

euvd junos_os fix: 23.2R2-S7.7, 23.4R2-S8.13, 24.2R2-S5.5, 24.4R2-S5, 25.2R2-S2, 25.4R1-S3, 26.2R1-S2
euvd junos_os_evolved fix: 23.2R2-S7.7-EVO, 23.4R2-S8.11-EVO, 24.2R2-S5.6-EVO, 24.4R2-S5-EVO, 25.2R2-S2-EVO, 25.2X100-D35-EVO, 25.4R1-S3-EVO, 25.4X300-D40-EVO, 26.2R1-S2-EVO

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 2 packages in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

The root cause is improper validation of consistency within input - the class of defects in which a parser accepts a message whose internal fields or attribute/ NLRI combinations are mutually inconsistent, deferring the failure to a downstream consumer that assumes consistency. Here the affected component is rpd, the Junos routing protocol daemon, and the input vector is the BGP ISO-VPN address family, the address family used to carry ISO/CLNS (IS-IS) reachability across a Layer 3 VPN. A specifically crafted ISO-VPN update is accepted and stored by the main BGP path, but when the same update is replayed or replicated onto a secondary processing path - BGP Monitoring Protocol (BMP) route monitoring, which streams Adj-RIB-In/route-monitoring copies to a collector, or Nonstop Active Routing (NSR), which checkpoints routing state between REs for hitless failover - the inconsistency is not tolerated and rpd aborts. The dual trigger condition explains the oddly asymmetric scored vector (affected system availability high, subsequent system availability low): the crash is local to the device, while the knock-on effect is loss of the monitoring feed or of NSR-protected redundancy. Adjacent protocols and neighboring devices are not implicated; the weakness is confined to rpd's ISO-VPN handling under BMP/NSR replication, and no CWE identifier was supplied in the source data.

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Severity by source

Vendor (juniper) PRIMARY 8.7 HIGH
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L
vuln.today AI 7.5 HIGH

Availability-only rpd crash (A:H, C:N/I:N) reachable over the network from a configured BGP ISO-VPN peer with no device authentication, hence PR:N and AC:L despite the peering/feature precondition.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (juniper).

CVSS VectorVendor: juniper

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Vulnerable system: Confidentiality
None
Vulnerable system: Integrity
None
Vulnerable system: Availability
High
Subsequent system: Confidentiality
None
Subsequent system: Integrity
None
Subsequent system: Availability
Low

Lifecycle Timeline

3
Patch available
Oct 14, 2026 - 19:35 EUVD
CVSS changed
Oct 14, 2026 - 18:22 NVD
7.5 (HIGH) 8.7 (HIGH)
CVE Published
Oct 14, 2026 - 17:21 cve.org
HIGH 8.7

DescriptionCVE.org

An Improper Validation of Consistency within Input vulnerability in the routing protocol daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows a configured BGP ISO-VPN peer to cause an rpd crash by sending a specific ISO-VPN update which is then processed by BMP route monitoring or NSR.

Executive ViewAI

Why It Matters

A high-severity availability issue affects Juniper Networks Junos OS and Junos OS Evolved routers that use BGP ISO-VPN peering and either BMP route monitoring or NSR replication. A malformed update from an established ISO-VPN peer can crash the routing protocol daemon and cause routing outages, potentially disrupting connectivity for customers, partners, and internal operations. No vendor-released patch identified at time of analysis, and no public exploit identified at time of analysis, so leadership should prioritize exposure assessment and interim mitigations for business-critical routing infrastructure.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis; interim mitigations include disabling BMP route monitoring or NSR replication on affected Juniper Networks Junos OS and Junos OS Evolved devices where operationally feasible, restricting BGP ISO-VPN peering to trusted peers, monitoring for rpd crashes, and maintaining redundant routing paths.

Threat Intelligence Overview

EPSS Score
0.4%
Top 70% exploitable
Prevalence
High
Junos OS/Evolved is widely deployed in enterprise and carrier routing networks
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.4%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
Yes
Human Impact
High
Technical Impact
Partial

Priority Score

44
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +44
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

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