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Weaponizing CVE-2026-1731: VShell and SparkRAT in Real-World BeyondTrust Breaches

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Executive Summary

On February 6, 2026, BeyondTrust disclosed a critical pre-authentication remote code execution vulnerability, CVE-2026-1731, affecting its Remote Support and Privileged Remote Access products. The flaw, assigned a CVSS v4 score of 9.9, enables unauthenticated attackers to execute arbitrary operating system commands through the exposed thin-scc-wrapper component over WebSocket connections.

Active exploitation has been observed in the wild, with attackers leveraging the vulnerability for initial access, web shell deployment, administrative account takeover, lateral movement, DNS-based command-and-control, and large-scale data exfiltration. Due to confirmed exploitation, the U.S. Cybersecurity and Infrastructure Security Agency (Cybersecurity and Infrastructure Security Agency) added CVE-2026-1731 to its Known Exploited Vulnerabilities (KEV) Catalog on February 13, 2026, mandating immediate remediation across U.S. federal networks.

Telemetry indicates more than 16,000 internet-exposed instances potentially vulnerable at the time of publication, significantly increasing the global attack surface.

Background on Malware, Backdoor and Threat Group

SparkRAT

SparkRAT is a cross-platform remote access trojan written in Go and publicly available as open-source software. First widely reported in 2023 during the DragonSpark campaigns, it supports Windows, Linux and macOS environments. Its modular design enables remote shell access, file management, command execution and encrypted C2 communications.

VShell

VShell is a stealth-oriented Linux backdoor characterized by:

  • Fileless execution in memory
  • Masquerading as legitimate system services
  • Persistent remote command execution
  • Evasion-focused tradecraft

Its use indicates post-compromise consolidation rather than opportunistic exploitation.

Historical Context and Threat Actor Links

CVE-2026-1731 shares technical similarities with CVE-2024-12356, a previously exploited WebSocket input validation flaw. That earlier vulnerability was leveraged by Silk Typhoon (also tracked as APT27/UNC5221/Emissary Panda) in high-profile intrusions, including the 2024 breach of the U.S. Treasury.

The recurrence of similar input validation weaknesses suggests that exposed remote access management planes remain high-value targets for sophisticated adversaries.

Vulnerability Details

CVE ID: CVE-2026-1731
Type: OS Command Injection (CWE-78)
Severity: Critical (CVSS v4: 9.9)
EPSS Score: 49.74%
Affected Products: BeyondTrust Remote Support (RS) version 25.3.1 and prior and Privileged Remote Access (PRA) version 24.3.4 and prior

Root Cause

The vulnerability exists in the thin-scc-wrapper component responsible for handling incoming WebSocket connections. During the connection handshake, the application processes a client-supplied parameter intended for version compatibility validation.

Due to insufficient input sanitization and improper handling within a shell evaluation context, the backend interprets attacker-controlled input as executable expressions rather than strictly as version data. This allows remote attackers to inject and execute arbitrary operating system commands without authentication.

The flaw stems from incomplete validation logic that failed to fully restrict expression evaluation within the version parsing routine.

Infection Method

The attack begins when a remote adversary initiates a WebSocket connection to an exposed BeyondTrust appliance. During the connection handshake, the attacker submits a specially crafted version parameter to the thin-scc-wrapper component.

Due to improper input validation, the backend processes this parameter in a way that allows attacker-controlled input to be interpreted as executable commands. As a result, arbitrary operating system commands are executed in the context of the site user.

Because this vulnerability is exploitable over the network and does not require authentication or user interaction, it enables direct remote code execution against exposed systems. The attack can be performed remotely against internet-facing instances, making unpatched deployments highly susceptible to compromise.

Impact

Successful exploitation of CVE-2026-1731 results in pre-authentication remote code execution (RCE) on affected BeyondTrust Remote Support and Privileged Remote Access appliances. Because the vulnerability is exploitable over the network without authentication, it significantly lowers the barrier to compromise.

The impact includes:

  • Network reconnaissance and domain enumeration
  • Temporary takeover of administrative accounts using custom tooling
  • Deployment of multiple web shells, including memory-resident and password-protected PHP backdoors
  • Installation of persistent backdoors and remote management tools, such as VShell and SparkRAT
  • Command-and-control (C2) communication, including DNS-based out-of-band validation techniques
  • Lateral movement across internal systems
  • Data staging and exfiltration, including configuration files, internal databases and full PostgreSQL dumps

The exploitation campaign has impacted organizations across financial services, legal services, high technology, higher education, wholesale and retail and healthcare sectors in the United States, France, Germany, Australia and Canada.

The similarity between CVE-2026-1731 and CVE-2024-12356 further underscores a recurring input validation weakness within exposed execution pathways. This pattern increases the risk that internet-facing remote management infrastructure will continue to be a prime target for both opportunistic and sophisticated threat actors.

Visual Flow

Exposed BeyondTrust Appliance -> Malicious WebSocket Handshake -> Version Parameter Injection -> Command Injection -> Pre-Auth RCE -> Web Shell -> SparkRAT / VShell Deployment -> C2 Communication -> Lateral Movement -> Data Exfiltration

Tactics Include

  • TA0001 – Initial Access: Exploitation of vulnerabilities to gain initial access to target systems.
  • TA0002 – Execution: Execution of arbitrary commands via injected payloads.
  • TA0003 – Persistence: Installation of web shells for maintaining access.
  • TA0004 – Privilege Escalation: Gaining elevated privileges through compromised accounts.

IOCs (Indicators of Compromise)

  • 23.162.40[.]187
  • 37.19.221[.]180
  • 45.61.150[.]96
  • 70.23.0[.]66
  • 82.29.53[.]187
  • 82.29.72[.]16
  • 83.138.53[.]139
  • 85.155.186[.]121
  • 92.223.44[.]134
  • 98.10.233[.]76
  • 134.122.13[.]34
  • 138.197.14[.]95
  • 142.111.152[.]50
  • 144.172.103[.]200/4444
  • 155.2.215[.]64
  • 178.128.212[.]209
  • 179.43.146[.]42
  • 45.61.150[.]96/4444
  • 138.197.14[.]95/ws (SparkRAT)
  • hxxp[:]//64.31.28[.]221/support
  • aliyundunupdate[.]xyz:8084/slt (VShell)
  • d65sb7ngveucv5k2nm508abdsjmbn7qmn.oast[.]pro
  • q0r2e5q2dzbykcox9qmkptm12s8mwb.oastify[.]com
  • hxxp[:]//134.122.13[.]34:8979/c (SparkRAT)
  • hxxp[:]//82.29.53[.]187:8778/app_cli
  • hxxps[:]//transfer.weepee[.]io/7nZw7/blue.drx
  • hxxp[://]85.155.186[.]121/access (SimpleHelp)
  • hxxps[:]//temp[.]sh/tQTSs/storm.exe
  • hxxps[:]//64.95.10[.]115:23011/update.sh
  • hxxps[:]//judiemkqjajsfzpidfjlowgl8nyrtd49x.oast[.]fun
  • hxxps[:]//raw.githubusercontent[.]com/nezhahq/scripts/main/agent/install.ps1
  • hxxp[:]//39uchxifap4cvgzsuirom0szrrg.d65lre9sfqnlcv49317gcis6pyjsatzho.oast[.]pro
  • hxxps[:]//85.155.186[.]121/access/Remote%20Access-linux64-offline.tar?language=en&app=76049110434275449312180081368257747094
  • hxxps[:]//github[.]com/nicocha30/ligolo-ng/releases/download/v0.8.2/ligolo-ng_agent_0.8.2_linux_amd64.tar.gz
  • 9f431d5549a03aee92cfd2bdbbe90f1c91e965c99e90a0c9ad5a001f4e80c350 (SparkRAT)
  • 98a7b0900a9072bb40af579ec372da7b27af12b15868394df51fefe290ab176b (VShell)
  • 66cceb2c2f1d9988b501832fd3b559775982e2fce4ab38fc4ffe71b74eafc726 (maintenance.php)
  • 679ee05d92a858b6fe70aeb6072eb804548f1732e18b6c181af122b833386afb (d6)
  • 4762e944a0ce1f9aef243e11538f84f16b6f36560ed6e32dfd9a5f99e17e8e50 (Installer for SimpleHelp)
  • 98442387d466f27357d727b3706037a4df12a78602b93df973b063462a677761 (aws.php)
  • cc2bc3750cc5125a50466f66ae4f2bedf1cac0e43477a78ed2fd88f3e987a292 (Bash Script)
  • cf83e1357eefb8bdf1542850d66d8007d620e4050b5715dc83f4a921d36ce9ce (file_save.php)
  • 0ecc867ce916d01640d76ec03de24d1d23585eb582e9c48a0364c62a590548ac

Mitigation & Recommendations:

  • Patch Product: BeyondTrust has released patches for affected versions; ensure all instances are updated to the latest versions as per the February 2026 advisory.
  • Restrict Access: Limit administrative interfaces to internal networks or implement zero trust network access gateways to reduce exposure.
  • Monitor Systems: Employ continuous monitoring for signs of exploitation and unauthorized access attempts.

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