CVE-2026-102176

Executive Summary

CVE-2026-102176 is a classic buffer overflow (CWE-120) in the SDK service process of Juniper Networks Junos OS that can be triggered by an unauthenticated network attacker sending specific packets when both the SDK service and a JDAF routing instance are enabled. Successful exploitation results in denial of service or compromise of the Routing Engine, carrying a CVSS 3.1 base score of 8.8 (High). Organizations running Junos OS with the SDK service and JDAF routing instances enabled are affected, and no patch or public proof-of-concept currently exists.

Technical Analysis

The vulnerability is classified as CWE-120, "Buffer Copy without Checking Size of Input," commonly referred to as a classic buffer overflow. In this class of flaw, a program copies input into a fixed-length buffer without validating that the input length does not exceed the buffer's capacity. When the source data is larger than the destination buffer, adjacent memory is overwritten, which can corrupt program state, crash the process, or — depending on memory layout and protections — enable controlled code execution.

The affected component is the SDK service process within Juniper Networks Junos OS. The attack surface is the network-facing packet handling path of that process. Per the NVD description, exploitation requires a specific operational precondition: the SDK service must be enabled and a JDAF routing instance must be configured. The attacker must be able to send packets to the affected service — the CVSS vector reflects an adjacent-network attack vector (AV:A), meaning the attacker must have network adjacency (e.g., a peering, transit, or otherwise reachable layer-2/layer-3 position relative to the vulnerable interface). The attack does not require authentication (PR:N) or user interaction (UI:N).

Because the flaw resides in packet processing logic, the trigger is a malformed or oversized packet — or sequence of packets — delivered to the SDK service. The precise packet structure, the specific field that overflows, and the memory-corruption mechanics are not disclosed in the available advisory text, so this report describes the vulnerability at the class level rather than fabricating function names, packet fields, or offsets. No public PoC, exploit code, or Nuclei template is available; the attack chain below is inferred from the vulnerability class.

Impact subscores are uniformly High (C:H/I:H/A:H) with Scope:Unchanged (S:U), indicating that a successful exploit impacts confidentiality, integrity, and availability of the vulnerable component while remaining within its security scope. The resulting outcome per the description is either denial of service or compromise of the Routing Engine.

Exploitation Scenarios

No public PoC is available; the following attack chain is inferred from the vulnerability class (CWE-120) and the description provided.

1. Reconnaissance / target identification. The attacker identifies a Juniper device running Junos OS that exposes the SDK service and has a JDAF routing instance enabled. Because the attack vector is adjacent (AV:A), the adversary must first obtain network reachability to the vulnerable interface — for example, by residing on a connected segment, a peering session, or an upstream/downstream transit path. Fingerprinting would focus on identifying Junos OS devices and confirming that the required service/instance configuration is present.

2. Triggering the flaw. The attacker sends "specific packets" to the SDK service. Because CWE-120 involves copying input without a size check, the trigger is data whose length exceeds the destination buffer's capacity. Sending an oversized or specially crafted packet causes the unchecked copy to overwrite memory beyond the intended buffer.

3. Payload / execution method (class level). The overflow corrupts adjacent memory in the SDK service process. At the class level, this manifests as either (a) an immediate crash/abnormal termination of the process — yielding denial of service — or (b) memory corruption that, if the overwritten data influences control flow or critical state, may lead to code execution within the context of the SDK service. The advisory explicitly frames the outcome as denial of service or compromise of the Routing Engine. No specific offsets, control-flow targets, or shellcode patterns are disclosed.

4. Post-exploitation impact. If only a crash is achieved, the result is a denial of service affecting routing functionality served by the device. If the corruption is leveraged further, the description indicates potential compromise of the Routing Engine — the control-plane component responsible for routing protocol operation and device management — which could allow disruption or manipulation of routing behavior. Specific post-exploitation capabilities are not enumerated in the available data.

Impact Assessment

The CVSS 3.1 base score is 8.8 (High) with vector CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

• Confidentiality: High (C:H) — compromise of the Routing Engine could expose routing and device data.
• Integrity: High (I:H) — a compromised control plane can alter routing state or device configuration.
• Availability: High (A:H) — the primary advertised impact is denial of service; the SDK service or the Routing Engine can be rendered unavailable.
• Attack Vector: Adjacent (AV:A) — the attacker requires network adjacency, not internet-wide reachability, which narrows the exposed population but is trivially satisfied by a peer or connected network.
• Attack Complexity: Low (AC:L), Privileges Required: None (PR:N), User Interaction: None (UI:N) — no credentials or victim action are needed once adjacency exists.

Blast radius. The affected component is a service process tied to Junos OS routing infrastructure. Because the process underpins SDK-related functionality and interacts with a JDAF routing instance, a successful attack can affect the device's routing operations — service providers and enterprises relying on the device for routing/peering are the primary at-risk population. The precondition (SDK service and a JDAF routing instance both enabled) limits exposure to configurations where those features are active.

Detection Guidance

Sigma Rule

title: Potential Junos OS SDK Service Buffer Overflow Exploitation Attempt (CVE-2026-102176)
id: 7f3c9a21-4b8e-4d6a-9c11-junos-sdk-bof
status: experimental
description: Detects anomalous process crashes or restart events in the Junos SDK service process that may indicate exploitation of CVE-2026-102176 (CWE-120 buffer overflow).
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-102176
author: valtersit.com
date: 2026/01/01
logsource:
  product: juniper
  service: junos
detection:
  selection_crash:
    process|contains: 'sdk'
    event_type|contains:
      - 'crash'
      - 'core'
      - 'restart'
      - 'segfault'
  selection_msg:
    message|contains:
      - 'SDK service'
      - 'core dump'
  condition: selection_crash or selection_msg
falsepositives:
  - Legitimate software upgrades or service restarts
level: high
tags:
  - attack.t1190
  - cve.2026.102176

YARA Rule

rule CVE_2026_102176_Junos_SDK_Overflow
{
    meta:
        description = "Detects referenced buffer overflow indicators for CVE-2026-102176 in Junos SDK service artifacts"
        author = "valtersit.com"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-102176"
        cve = "CVE-2026-102176"
        date = "2026-01-01"

    strings:
        $sdk = "SDK" ascii wide nocase
        $junos = "Junos" ascii wide nocase
        $jdaf = "JDAF" ascii wide nocase
        $overflow_hint = "buffer copy" ascii wide nocase

    condition:
        uint16(0) == 0x5A4D or
        (2 of ($sdk, $junos, $jdaf, $overflow_hint))
}

Suricata IDS Rule

alert ip any any -> any any (msg:"CVE-2026-102176 Junos OS SDK Service Potential Buffer Overflow - Large Anomalous Packet"; flow:to_server; dsize:>1400; byte_test:1,&,0xFF,0,relative; threshold:type both, track by_src, count 10, seconds 5; classtype:attempted-dos; reference:cve,2026-102176; metadata:affected_product Juniper_Junos_OS; sid:2026102176; rev:1;)

Elastic Detection

process where process.name : "sdk*" and
  (event.action : ("crash", "segfault") or
   message : ("*core dump*", "*SDK service*crash*", "*stack smashing*"))

Splunk SPL Query

index=junos sourcetype=juniper:junos
| search ("SDK" OR "sdk") AND ("crash" OR "core" OR "segfault" OR "restart" OR "buffer")
| stats count min(_time) as firstSeen max(_time) as lastSeen by host, process, message
| where count >= 1
| convert ctime(firstSeen) ctime(lastSeen)

Wazuh OSSEC Rule

<group name="juniper,junos,">
  <rule id="1021760" level="12">
    <decoded_as>json</decoded_as>
    <field name="process">sdk</field>
    <match>crash|core dump|segfault|SDK service</match>
    <description>CVE-2026-102176: Possible Junos OS SDK service buffer overflow exploitation (crash/DoS)</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>cve_2026_102176,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source).

1. Immediate mitigations.

   • Disable the SDK service if it is not operationally required; the vulnerability is only reachable when the SDK service is enabled.
   • Where feasible, remove/disable JDAF routing instances, since the advisory states exploitation requires both the SDK service and a JDAF routing instance to be enabled.
   • Restrict network adjacency to the affected service using interface ACLs/firewall filters so only trusted, required peers can reach the device, reducing the AV:A attack surface.
   • Monitor for repeated crashes/restarts of the SDK service process as an early indicator.

2. Patch / upgrade steps.

   • No vendor patch is available as of this report (patch confidence 0/4). Track the Juniper Networks security advisories portal for an official fix and apply the vendor-recommended Junos OS release as soon as it is published.
   • When a patched release is issued, upgrade affected devices following Juniper's standard upgrade procedures and validate that the SDK service/JDAF configuration remains as intended.

3. Long-term hardening.

   • Adopt least-exposure network design: keep control-plane services reachable only from trusted management/peer networks.
   • Inventory devices running Junos OS with SDK service or JDAF routing instances enabled and prioritize them for monitoring.
   • Maintain a patch-management process with defined SLAs for High-severity, unauthenticated, network-adjacent vulnerabilities.
   • Enable robust logging and forwarding to a SIEM so control-plane process crashes are detected and correlated.

References

• NVD — CVE-2026-102176: https://nvd.nist.gov/vuln/detail/CVE-2026-102176
• MITRE CWE-120 — Buffer Copy without Checking Size of Input: https://cwe.mitre.org/data/definitions/120.html
• Juniper Networks Security Advisories (SIRT): https://supportportal.juniper.net/s/global-search/%40uri#security-advisories
• FIRST CVSS v3.1 Specification: https://www.first.org/cvss/v3.1/specification-document
• CISA Known Exploited Vulnerabilities Catalog (CVE-2026-102176 not listed): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

No public exploit code, PoC, or Nuclei template is available for CVE-2026-102176. The CVE is not listed in CISA KEV, and no confirmed threat-actor campaign or in-the-wild exploitation evidence was identified in the available data at the time of writing.