CVE-2026-111853

Executive Summary

CVE-2026-111853 is an OS command injection vulnerability (CWE-78) in the SCPI command handler of Tektronix 3 Series MDO mixed-domain oscilloscopes running firmware before 1.21.1. The flaw lies in the FILESystem:MOUNT:DRIve command, where insufficient neutralization of user-supplied input allows a remote attacker to execute arbitrary operating system commands with elevated privileges. With a CVSS base score of 8.8 and a network-reachable attack vector requiring only low privileges, this vulnerability is a serious risk for any organization exposing Tektronix MDO devices on lab, engineering, or production networks.

Technical Analysis

The vulnerability class is OS command injection (CWE-78). Tektronix 3 Series MDO instruments expose a SCPI (Standard Commands for Programmable Instruments) interface used for remote control and automation. The FILESystem:MOUNT:DRIve SCPI command is intended to mount or select a storage drive (e.g., internal memory, USB media). Because the handler passes user-supplied input into an underlying operating system command without proper neutralization/escaping, an attacker who can issue SCPI commands can append or inject shell metacharacters that the device's OS interprets and executes.

Key attributes from the CVSS vector (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H):

• AV:N (Network) — the SCPI interface is reachable over the network, so no physical/local access to the front panel is required.
• AC:L (Low) — no special conditions or race timing are needed.
• PR:L (Low) — the attacker must be able to issue commands to the SCPI interface (e.g., authenticated or otherwise authorized SCPI session), not fully unauthenticated.
• UI:N — no user interaction required.
• S:U (Unchanged) — impact is scoped to the vulnerable instrument.
• C/I/A: H/H/H — full compromise of confidentiality, integrity, and availability of the device.

The exact parsing routine, escape behavior, and injection metacharacters are not detailed in the available NVD description. What is technically determinable is the vulnerability class and reachability: a SCPI command that proxies into an OS-level operation, fed untrusted input, yields command injection. The precise internal code paths and parameters are not publicly documented.

Because the injected commands execute "with elevated privileges" per the description, successful exploitation can yield high-integrity command execution on the instrument's embedded operating system — a significant escalation beyond the normal measurement/control functions of the scope.

Exploitation Scenarios

No public PoC, Nuclei template, or exploit code is available. The attack chain below is inferred at the vulnerability-class level from the NVD description; no specific command syntax or parameter names beyond FILESystem:MOUNT:DRIve are asserted.

1. Reconnaissance / target identification. The attacker identifies reachable Tektronix 3 Series MDO devices on the network — typically instruments exposing a SCPI control channel (commonly associated with VXI-11/raw TCP port 5025 and HTTP-based control pages, though the exact transport is not specified in the advisory). Asset inventory and Shodan-style product fingerprinting ("Tektronix", "3 Series MDO") help locate exposed units. Lab and test-bench networks frequently leave instruments exposed with weak or default access because they are treated as "non-IT" assets.

2. Triggering the flaw class. Once the attacker can send SCPI commands to the device, they target the FILESystem:MOUNT:DRIve command handler. The handler fails to neutralize untrusted input before passing it to an OS-level operation. By supplying crafted input containing shell-control characters, the attacker causes the embedded OS to interpret attacker-controlled text as an additional command. (At the class level: this is classic OS command injection — user input concatenated into a shell invocation without escaping.)

3. Payload / execution. The injected OS command runs with the elevated privileges described in the advisory. The attacker uses this to run arbitrary operating-system commands on the instrument. Specific payload construction is not documented publicly; the essential mechanism is untrusted SCPI input reaching an OS command with elevated rights.

4. Post-exploitation impact. With elevated command execution, an attacker can read, modify, or destroy data on the device (integrity and confidentiality High), disrupt instrument availability (availability High), pivot from the instrument into the broader engineering/test network, and manipulate measurement results or stored captures — a serious concern where instruments feed calibration, QA, or compliance workflows.

Impact Assessment

CVSS 8.8 (High). Exploitation requires network reachability and a low-privileged SCPI session (PR:L), with no user interaction (UI:N). The scope is unchanged (S:U), but all three CIA pillars are rated High — the instrument itself is fully compromised once the injected command executes.

Affected systems: Tektronix 3 Series MDO oscilloscopes running firmware before 1.21.1. These are specialized test-and-measurement instruments typically found in engineering labs, hardware validation benches, manufacturing/QA lines, and R&D environments.

Blast radius: Because the injected command runs with elevated privileges, an attacker can gain a foothold on the instrument and use it as a pivot into lab or OT-adjacent networks. Integrity impact is particularly concerning for measurement instruments — tampered or falsified measurements can propagate into product validation, calibration records, and compliance evidence. Availability impact can halt testing workflows; confidentiality impact can expose captured signal data, network details, and potentially credentials or configuration stored on the device.

No CISA KEV listing and no EPSS score are available; exploitability in the wild is currently unconfirmed. The combination of network exposure, low attack complexity, and only low privileges required makes this attractive to adversaries who find instruments on poorly segmented networks.

Detection Guidance

Sigma Rule

title: Tektronix 3 Series MDO SCPI FILESystem MOUNT DRIve Command Injection
id: 8f2c1a4e-3b7d-4c9a-9e21-tek3mdo01
status: experimental
description: Detects SCPI FILESystem:MOUNT:DRIve commands containing shell metacharacters indicative of OS command injection against Tektronix 3 Series MDO devices.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-111853
author: Threat Intelligence
date: 2026/01/01
logsource:
  category: network_connection
  product: suricata
detection:
  selection_cmd:
    payload|contains: 'FILESystem:MOUNT:DRIve'
  selection_inject:
    payload|contains:
      - ';'
      - '|'
      - '&&'
      - '`'
      - '$('
      - '>/'
      - '>/tmp'
  condition: selection_cmd and selection_inject
falsepositives:
  - Legitimate automation using unusual characters in drive strings
level: high
tags:
  - attack.t1190
  - cwe.78

YARA Rule

rule CVE_2026_111853_Tektronix_SCPI_CmdInjection
{
    meta:
        description = "Detects SCPI FILESystem:MOUNT:DRIve command injection attempts targeting Tektronix 3 Series MDO"
        reference = "CVE-2026-111853"
        cwe = "CWE-78"
        author = "Threat Intelligence"
        date = "2026-01-01"

    strings:
        $scpi = "FILESystem:MOUNT:DRIve" ascii nocase
        $scpi2 = "FILESystem:MOUNT" ascii nocase
        $meta1 = ";/" ascii
        $meta2 = "&&" ascii
        $meta3 = "$(" ascii
        $meta4 = "`" ascii

    condition:
        ($scpi or $scpi2) and 1 of ($meta*)
}

Suricata IDS Rule

alert tcp any any -> any any (msg:"CVE-2026-111853 Tektronix 3 Series MDO SCPI FILESystem:MOUNT:DRIve Command Injection Attempt"; flow:to_server,established; content:"FILESystem:MOUNT"; nocase; content:"DRIve"; nocase; distance:0; pcre:"/FILESystem:MOUNT:DRIve[^\r\n]*(?:;|\||&&|\$\(|`)/i"; reference:cve,2026-111853; classtype:web-application-attack; sid:2026111853; rev:1;)

Elastic Detection

network where process.name != null and
  network.protocol in ("tcp") and
  string(network.packet_payload).contains("FILESystem:MOUNT:DRIve") and
  (string(network.packet_payload).contains(";") or
   string(network.packet_payload).contains("&&") or
   string(network.packet_payload).contains("$(") or
   string(network.packet_payload).contains("`"))

Splunk SPL Query

index=network sourcetype=suricata OR sourcetype=zeek
| eval p=coalesce(payload, raw)
| where match(p, "(?i)FILESystem:MOUNT:DRIve") AND match(p, "(?i)(;|\|\||&&|\$\(|`)")
| stats count earliest(_time) as first_seen latest(_time) as last_seen by src_ip dest_ip dest_port
| where count > 0

Wazuh OSSEC Rule

<group name="tektronix,scpi_cmd_injection,">
  <rule id="2026111" level="12">
    <decoded_as>json</decoded_as>
    <field name="scpi_command">FILESystem:MOUNT:DRIve</field>
    <regex type="pcre2">(?i)FILESystem:MOUNT:DRIve.*(;|\|\||&&|\$\(|`)</regex>
    <description>CVE-2026-111853: Tektronix 3 Series MDO SCPI OS command injection attempt detected</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>attack,cwe_78,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source). The NVD description indicates the fix is firmware version 1.21.1, but no independent patch reference, advisory link, or vendor source has been confirmed in the tracked data; treat the version threshold as sourced from the description only and verify against the vendor before relying on it.

1. Immediate mitigations. Restrict network access to SCPI/control interfaces on 3 Series MDO devices so only authorized engineering hosts can connect. Segment instruments onto dedicated, firewalled management/VLANs isolated from general IT and the internet. Enforce authentication on remote-control channels, eliminate default or weak credentials, and block all inbound access to instrument control ports at the perimeter.
2. Patch / upgrade. Apply Tektronix firmware 1.21.1 or later to affected 3 Series MDO devices as indicated by the advisory, validating the version through official vendor channels. Inventory all instruments and confirm firmware levels; prioritize units that are network-exposed.
3. Long-term hardening. Treat test-and-measurement instruments as managed assets with firmware-patch cadence, configuration baselining, and logging. Apply least-privilege and allow-list controls to SCPI traffic, monitor instrument networks for command-injection patterns (as in the detection rules above), and include lab/OT devices in vulnerability management and network monitoring rather than leaving them as unmanaged "appliances."

References

• NVD — CVE-2026-111853: https://nvd.nist.gov/vuln/detail/CVE-2026-111853
• Tektronix product/security support portal (3 Series MDO firmware): https://www.tek.com/
• MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
• MITRE CWE-78 — Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection'): https://cwe.mitre.org/data/definitions/78.html
• CISA KEV catalog (no entry for CVE-2026-111853 at time of writing): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

No confirmed threat-actor campaign or exploit-in-the-wild evidence is currently available for this CVE; no public PoC, Nuclei template, or exploit code was identified, and no EPSS score has been assigned.