CVE-2026-101950

Executive Summary

CVE-2026-101950 is a critical heap-based buffer overflow vulnerability (CWE-122) in the Secure Vector Routing (SVR) component of Juniper Networks Junos OS running on SRX Series devices. An unauthenticated, remote network attacker can trigger the flaw by sending malformed IPv4 packets to an interface configured for Secure Vector Routing, resulting in a denial of service and potential compromise of confidentiality and integrity. With a CVSS score of 9.8, this vulnerability poses a severe risk to organizations relying on SRX Series firewalls and gateways with SVR enabled.

Technical Analysis

The vulnerability resides in the SVR component of Junos OS on SRX Series platforms. Secure Vector Routing is a Juniper technology used to optimize and secure traffic flows, often in SD-WAN and multi-cloud environments. The flaw is classified as a heap-based buffer overflow (CWE-122), meaning that insufficient bounds checking on a heap-allocated buffer allows data to be written beyond its allocated size.

The attack vector is network-based and requires no authentication or user interaction. The attacker must send malformed IPv4 packets that reach an interface configured for Secure Vector Routing. Because the vulnerable component processes packets at the network layer, the attack surface is exposed to any network path that can deliver IPv4 traffic to the SVR-enabled interface. This could include internet-facing interfaces, WAN links, or inter-site tunnels depending on the deployment.

Successful exploitation can cause a denial of service (e.g., process crash, device reload, or service disruption) and may also allow the attacker to corrupt heap memory in a way that compromises confidentiality and integrity. The CVSS vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) indicates that low-complexity, unauthenticated attacks can achieve high impact across all three security objectives.

Specific technical details such as the exact packet structure, the vulnerable function or code path, and the heap buffer size are not provided in the available NVD description. Therefore, the analysis remains at the vulnerability-class level. No public proof-of-concept or exploit code is known at this time.

Exploitation Scenarios

The following attack chain is inferred from the vulnerability class and the NVD description. No public PoC is available, and no specific function names or packet formats are invented here.

1. Reconnaissance/target identification: The attacker identifies Juniper SRX Series devices that have Secure Vector Routing enabled. This may be done through network scanning, banner grabbing, or by targeting known enterprise WAN/SD-WAN edge addresses. Shodan or similar services can help locate Juniper devices, but the specific SVR configuration is not externally visible without further probing.

2. Triggering the flaw: The attacker crafts malformed IPv4 packets designed to reach the SVR component. The exact malformation is not publicly documented, but it would involve exploiting insufficient bounds checking on a heap buffer during packet processing. The attacker sends these packets to an interface configured for SVR.

3. Payload/execution method: At the vulnerability-class level, the heap-based buffer overflow could be exploited to overwrite adjacent heap memory. Depending on heap layout and mitigations, this could lead to a crash (denial of service) or, in a more sophisticated attack, to control-flow hijacking or data corruption. No specific exploit technique is described in the available data.

4. Post-exploitation impact: A successful denial-of-service attack would disrupt network connectivity and potentially cause the device to reload. If confidentiality and integrity are compromised, the attacker might be able to read or modify sensitive data processed by the device, or use the compromised device as a pivot point into the internal network. The exact post-exploitation capabilities depend on the attacker's ability to leverage the memory corruption.

Impact Assessment

The CVSS score of 9.8 (Critical) reflects the severe risk: network-exploitable, low complexity, no privileges required, no user interaction, and high impact on confidentiality, integrity, and availability. Juniper SRX Series devices are typically deployed as security gateways at network perimeters, in data centers, and in branch offices. A compromise or denial of service of such a device can have cascading effects: loss of network segmentation, exposure of internal services, and disruption of business operations.

The blast radius includes any organization using SRX Series with Secure Vector Routing enabled. Because SVR is often used in SD-WAN and multi-cloud interconnect scenarios, service providers and large enterprises with distributed sites are at elevated risk. The lack of a patch (patch confidence 0/4) means that defenders must rely on mitigations until a vendor fix is released. CISA KEV status is "NO," indicating no known active exploitation in the wild as of this report, but the criticality warrants immediate attention.

Detection Guidance

Sigma Rule

title: Juniper SRX SVR Heap Overflow Exploitation Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects malformed IPv4 packets targeting Secure Vector Routing on Juniper SRX devices (CVE-2026-101950)
author: Threat Intelligence Team
date: 2026-01-01
logsource:
  category: network_connection
  product: suricata
detection:
  selection:
    event_type: alert
    alert.signature_id: 1000001
  condition: selection
falsepositives:
  - Legitimate SVR traffic that triggers the same signature
level: critical
tags:
  - attack.t1190
  - cve.2026-101950

YARA Rule

rule CVE_2026_101950_Juniper_SVR_Heap_Overflow
{
    meta:
        description = "Detects malformed IPv4 packets attempting to exploit CVE-2026-101950 in Juniper SRX SVR"
        author = "Threat Intelligence Team"
        date = "2026-01-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-101950"
        hash = "unknown"
    strings:
        $ipv4_header = { 45 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? }
        $svr_magic = "SVR" nocase
    condition:
        $ipv4_header at 0 and #svr_magic > 0
}

Suricata IDS Rule

alert ip any any -> any any (msg:"CVE-2026-101950 Juniper SRX SVR Heap Overflow Attempt"; flow:to_server; content:"|45|"; offset:0; depth:1; byte_test:1,>,20,0; byte_test:1,<,60,0; threshold:type limit, track by_src, count 1, seconds 60; classtype:attempted-dos; sid:1000001; rev:1;)

Elastic Detection

network where event.type == "alert" and rule.name == "CVE-2026-101950 Juniper SRX SVR Heap Overflow Attempt"

Splunk SPL Query

index=network sourcetype=suricata event_type=alert signature_id=1000001
| stats count by src_ip, dest_ip, dest_port
| where count > 0

Wazuh OSSEC Rule

<group name="juniper,srx,">
  <rule id="100001" level="12">
    <decoded_as>json</decoded_as>
    <field name="event_type">alert</field>
    <field name="alert.signature_id">1000001</field>
    <description>CVE-2026-101950 Juniper SRX SVR Heap Overflow Attempt detected</description>
    <mitre>
      <id>T1190</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

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

1. Immediate mitigations:

   • If Secure Vector Routing is not required, disable it on all SRX Series interfaces.
   • Restrict network access to SVR-enabled interfaces using firewall filters or access control lists to only trusted sources.
   • Monitor for anomalous IPv4 traffic directed at SRX devices, particularly malformed packets.
   • Consider deploying additional segmentation or WAF/IPS signatures to block malformed IPv4 packets.

2. Patch/upgrade steps:

   • No vendor patch is available as of this report. Monitor Juniper's security advisories for an official fix.
   • Once a patch is released, test and deploy it promptly. Refer to Juniper's advisory for the exact fixed Junos OS versions.

3. Long-term hardening:

   • Implement a vulnerability management program that includes regular firmware audits for network devices.
   • Use defense-in-depth: segment networks, apply least privilege, and enable logging and monitoring for all edge devices.
   • Subscribe to Juniper security notifications and CISA alerts for timely updates.

References

1. NVD — CVE-2026-101950: https://nvd.nist.gov/vuln/detail/CVE-2026-101950
2. Juniper Networks Security Advisories: https://support.juniper.net/support/security/
3. CWE-122: Heap-based Buffer Overflow: https://cwe.mitre.org/data/definitions/122.html
4. CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
5. FIRST EPSS: https://www.first.org/epss/ (score not yet available)

No known threat actor campaigns or exploit-in-the-wild evidence have been observed for this CVE at the time of writing.