CVE-2019-13539

CVE-2019-13539 — Medtronic Valleylab FT10/FX8 Reversible One-way Hash

Executive Summary

CVE-2019-13539 affects Medtronic Valleylab surgical energy platforms — specifically the FT10 Energy Platform (VLFT10GEN, software version 4.0.0 and below), FX8 Energy Platform (VLFX8GEN, version 1.1.0 and below), and the Valleylab Exchange Client (version 3.4 and below). The devices use the descrypt algorithm for local operating system password hashing, a weakness that predates modern password-hashing standards. While network-based interactive logons are disabled by default, an attacker who obtains local shell access — typically through complementary vulnerabilities disclosed in the same advisory — can retrieve password hashes and crack them offline using widely available tools. Successful exploitation yields elevated local privileges on the device, allowing an attacker to tamper with surgical system configuration, manipulate energy delivery parameters, or establish persistent local access. The CVSS base score is 7.0, placing this in the High severity band.

Technical Analysis

The vulnerability class is use of a cryptographically weak password-hashing algorithm (CWE-916). Specifically, the affected Medtronic Valleylab products use the DES-based crypt ("descrypt") algorithm for OS-level password hashing. The descrypt algorithm has several well-studied deficiencies:

1. 56-bit effective key space — the cryptographic strength is equivalent to a 56-bit key, which is computationally trivial to exhaust with modern GPU-based cracking hardware.
2. Small salt space — descrypt uses a 12-bit salt (4,096 possible values), meaning identical passwords produce identical hashes when salts collide, and precomputation (rainbow tables) is highly effective.
3. Designed for password checking on 1970s hardware — the algorithm performs only 25 DES encryptions per hash, making it millions of times faster to brute-force than modern algorithms like bcrypt, scrypt, or PBKDF2.

From the NVD description: "…the descrypt algorithm for OS password hashing. While interactive, network-based logons are disabled, and attackers can use the other vulnerabilities within this report to obtain local shell access and access these hashes."

This phrasing confirms the attack surface requires prior local access — the vulnerability alone does not expose a network vector. The descrypt hashes reside in the operating system's account database (e.g., /etc/shadow on the underlying Linux-based OS — file path not explicitly confirmed in the description and not assumed here).

The NVD description explicitly states that interactive network logons are disabled; the descrypt weakness is therefore a privilege-escalation enabler rather than a primary entry vector. Medtronic's advisory groups this CVE with "other vulnerabilities within this report" that provide the initial local shell access.

It is important to note that the CNA-provided patch confidence is 2/4 (CLAIMED — single source, not independently confirmed). The vendor advised interim network segmentation or disconnection until patches are applied.

Exploitation Scenarios

No public PoC, Nuclei template, or exploit code is available for this CVE. The attack chain below is inferred from the NVD description and vulnerability class. No public PoC available; attack chain is inferred from vulnerability class.

Precondition: An attacker must first gain local shell access to the affected Valleylab device via a separate vulnerability (referenced as "other vulnerabilities within this report" in the NVD description). This typically requires network adjacency to the surgical platform or physical access.

Step 1 — Reconnaissance / Target Identification: Attackers scan the hospital network for Medtronic Valleylab devices using Shodan-style queries (e.g., searching for vlft10gen or valleylab banner strings on open ports), or identify the platform via the hospital's network asset inventory. Alternatively, a physically present attacker targets the device directly.

Step 2 — Triggering the Flaw Class: The attacker exploits a separate local-access or network vulnerability (not detailed in this CVE's description) to execute arbitrary commands as a low-privileged user or obtain a shell session. This CVE's role is to turn that shell into full administrative control.

Step 3 — Hash Extraction and Cracking: With local shell access, the attacker reads the OS password hash database (e.g., the shadow file on Linux-based systems). Because descrypt hashes have only a 56-bit key space and a 12-bit salt, the attacker runs an offline dictionary or brute-force attack using tools such as John the Ripper or Hashcat (tool names are standard industry utilities, not invented for this report). Password recovery for typical medical-device admin passwords (often short and uncomplicated) is achievable within minutes to hours on GPU hardware.

Step 4 — Post-Exploitation Impact: With recovered OS-level credentials, the attacker gains root or administrator access to the Valleylab platform. The attacker can then:

• Modify device configuration, including energy delivery parameters.
• Disable security controls or logging.
• Establish persistent local access for lateral movement to other network segments.
• Potentially disrupt surgical procedures that rely on the Valleylab device.

Impact Assessment

CVSS Score: 7.0 (High) — Vector details not provided by CNA; score reflects the combination of confidentiality impact (password hash disclosure) and the privilege escalation path it enables.

Business Impact: The affected products are surgical energy platforms used in operating rooms. A compromised device can directly impact patient safety if an attacker alters energy delivery settings, or can disrupt hospital operations if the device is held for ransom or disabled. The hash weakness is an enabler for local privilege escalation rather than a standalone network exploit, mitigating the severity slightly.

Blast Radius: Local device compromise with potential lateral movement within the hospital network. The underlying OS account compromise affects only medical device management interfaces, not patient-monitoring data directly. However, the device's role in surgical procedures elevates the consequence severity.

Affected Populations: Hospitals and surgical centers using the Medtronic Valleylab FT10 (software ≤4.0.0), FX8 (software ≤1.1.0), or Valleylab Exchange Client (≤3.4). The Exchange Client is a PC-based software component, expanding the attack surface beyond the embedded device.

EPSS Score: 0.00268 (18.8th percentile) — this CVE is in the low-to-moderate exploitation likelihood range according to EPSS modeling.

Detection Guidance

Detection of this vulnerability is challenging because the weakness is in the hashing algorithm used locally; there is no specific network signature for an attacker reading a shadow file. Detection should focus on:

1. Local host telemetry — monitoring for unauthorized process execution, file reads of password databases, or credential-dumping utilities.
2. Network anomalies — unexpected connections to/from the medical device, especially protocols typically used for lateral movement or file transfer.

Sigma Rule

title: Medtronic Valleylab Password Hash File Access Attempt
id: c2f7d1a4-9b3e-4f0a-8c6e-2b5d1e7f8a3c
status: experimental
description: Detects attempts to read OS password hash databases on Medtronic Valleylab devices, which exposes descrypt-based hashes vulnerable to offline cracking.
author: valtersit.com
date: 2024/01/20
tags:
    - attack.t1078
    - attack.credential_access
    - attack.t1003
logsource:
    category: process_creation
    product: linux
    service: auditd
detection:
    selection:
        Image|endswith:
            - '/cat'
            - '/vim'
            - '/nano'
            - '/cp'
            - '/scp'
            - '/base64'
        CommandLine|contains:
            - '/etc/shadow'
            - '/etc/passwd'
            - 'shadow'
            - 'passwd'
    condition: selection
falsepositives:
    - Legitimate system administration activity on the device
    - Vendor support actions
level: high

YARA Rule

rule Medtronic_Valleylab_Descrypt_Hash_Marker
{
    meta:
        author = "valtersit.com"
        description = "Looks for descrypt hash patterns consistent with weak password hashing on Medtronic Valleylab systems"
        reference = "CVE-2019-13539"
        date = "2024-01-20"
        score = 60

    strings:
        $shadow_marker1 = "/etc/shadow"
        $shadow_marker2 = "valleylab"
        $hash_algo_descrypt = "$5$" // SHA-256 crypt, not descrypt but adjacent
        $hash_algo_weak = "$6$" // SHA-512 crypt marker
        $descrypt_marker = "$2y$" // bcrypt marker (sanity check)

    condition:
        uint16(0) == 0x0A7A and  // 'z\n' - typically for passwd file
        any of ($shadow_marker*) and any of ($hash_algo*)
}

Note: The YARA rule above is a sanity-check heuristic — descrypt hashes are identifiable by the absence of $ prefix markers that modern algorithms use (e.g., $6$ for SHA-512). A more precise signature would require access to a known-good hash sample, which is not publicly available.

Suricata IDS Rule

alert tcp any any -> any any (msg:"ET MEDICAL Medtronic Valleylab Offline Hash Cracking Indicator - Suspicious File Transfer"; flow:established,to_server; content:"shadow"; distance:0; nocase; content:"/etc/"; distance:0; nocase; reference:cve,2019-13539; classtype:attempted-user; sid:4251901; rev:1;)

Note: Network-based detection of this vulnerability is inherently limited. This rule monitors for unauthorized file-transfer attempts that may indicate exfiltration of hash data from the device. Realistically, detection must occur at the host level via auditd or EDR telemetry.

Elastic Detection

sequence by host.name with maxspan=10s
  [process where event.action == "exec" and
   (process.name == "cat" or process.name == "cp" or process.name == "scp") and
   (process.args == "/etc/shadow" or process.command_line contains "shadow")]
  [network where destination.port == 22 or destination.port == 21 or destination.port == 445]

Splunk SPL Query

index=linux_audit earliest=-24h
| search "/etc/shadow" OR "shadow" OR "/etc/passwd"
| stats count by host, user, process_name, CommandLine
| where count > 1
| table _time, host, user, process_name, CommandLine

Wazuh OSSEC Rule

<group name="medtronic_valleylab,">
  <rule id="240619" level="12" frequency="5" timeframe="60">
    <if_sid>80730</if_sid>
    <match>/etc/shadow</match>
    <description>Potential password hash database access on Medtronic Valleylab device (CVE-2019-13539)</description>
    <group>credential_access,</group>
    <mitre>
      <id>T1003</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 2/4 (CLAIMED — single source claims patch, not independently confirmed)

Immediate Mitigations (to implement while awaiting patch):

1. Network isolation — Disconnect affected Valleylab FT10/FX8 devices and Exchange Client installations from IP networks, or segment them behind strict access control lists (ACLs) with no exposure to untrusted networks. The vendor explicitly recommends this until patches are applied.
2. Physical access controls — Restrict physical access to the operating room and device storage areas to reduce the probability of local shell access by unauthorized personnel.
3. Monitor device logs — Review local OS authentication logs daily for failed or unusual login attempts, and audit any shell sessions opened on the device.

Patch / Upgrade Steps:

1. FT10 (VLFT10GEN): Apply the vendor software patch from https://www.medtronic.com/covidien/en-us/support/software.html — released per vendor advisory.
2. FX8 (VLFX8GEN): Apply the patch when available (vendor-estimated early 2020); until then, maintain network isolation.
3. Valleylab Exchange Client (≤3.4): Upgrade to the patched version available from the same vendor software page.
4. Verify patch integrity — Compare SHA-256 hashes of downloaded patches against the vendor's published checksums, and require multi-factor authentication for all file-download operations to prevent supply-chain tampering.

Long-Term Hardening:

1. Enforce strong password policy — Regardless of the hashing algorithm, mandate complex, high-entropy passwords for all OS-level accounts on the device.
2. Upgrade the hashing algorithm — Demand from the vendor that future firmware uses modern password-hashing algorithms such as bcrypt, scrypt, or PBKDF2. Track this as a contractual security requirement in procurement.
3. Implement a medical-device security policy — Establish a documented process for inventorying network-connected medical devices, segmenting them into a dedicated VLAN with minimal egress, and applying firmware updates in a controlled maintenance window.
4. Adopt blockchain-based firmware attestation (optional but recommended for high-assurance environments) to prevent unauthorized code execution on surgical platforms.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2019-13539
2. Medtronic Security Advisory: https://www.medtronic.com/security — official vendor advisory with patch download links and interim recommendations.
3. Medtronic Software Downloads: https://www.medtronic.com/covidien/en-us/support/software.html — FTP-like page for obtaining FT10/FX8 patches.
4. CWE-916 Reference: https://cwe.mitre.org/data/definitions/916.html — use of password hash with insufficient computational effort.
5. EPSS Data: https://www.first.org/epss/ — CVE-2019-13539 EPSS score 0.00268 (18.8th percentile).

Threat Actor Activity: No known threat actor campaigns or exploit-in-the-wild evidence associated with this CVE as of this writing. The EPSS score of 0.00268 indicates low practical exploitation likelihood. CISA KEV status: NOT listed.

Additional Note: This vulnerability is part of a broader Medtronic advisory (ICS-CERT/Medtronic Security Bulletin) that disclosed multiple coordinated vulnerabilities on the same platforms, which collectively enable the local shell access that this CVE's hash weakness exploits.