CVE-2021-27501

Executive Summary

CVE-2021-27501 affects Philips Vue PACS versions 12.2.x.x and prior, a medical imaging platform widely deployed in hospital environments for picture archiving and communication. The vulnerability stems from the vendor's failure to adhere to secure coding standards during development, which can introduce resultant weaknesses or amplify the severity of other associated vulnerabilities. With a CVSS score of 7.5, successful exploitation could lead to data integrity compromise, unauthorized access to sensitive patient imaging data, or service disruption. Philips has announced remediation via Version 15, scheduled for Q1/2022, with configuration hardening guidance provided as an interim control.

Technical Analysis

The NVD description for CVE-2021-27501 cites "improper adherence to coding standards" in Philips Vue PACS — a systemic development-process deficiency rather than a single software defect. The CWE-710 (Improper Adherence to Coding Standards) weakness class indicates that the software was developed without consistently following established secure coding rules, leading to a condition where resultant weaknesses may emerge at various points across the product's attack surface.

This vulnerability class is particularly significant in medical device software due to the regulatory frameworks (e.g., FDA premarket requirements) that mandate secure development lifecycle practices. The broad scope of this weakness means that the actual exploitable condition(s) may vary depending on the specific code paths in the affected version. Possible manifestations of such coding-standard deficiencies include buffer overflows, improper input validation, insecure cryptographic implementations, or unsafe error handling — all of which could be chained with other vulnerabilities to achieve greater impact.

The affected product family is Philips Vue PACS (Picture Archiving and Communication System), a centralized diagnostic imaging platform that stores, retrieves, distributes, and presents medical images (e.g., X-ray, MRI, CT, ultrasound) to radiologists and clinicians. Versions 12.2.x.x and earlier are confirmed vulnerable. The attack surface includes the PACS server endpoints accessible to clinical workstations and, in many deployments, hospital network segments that may be exposed to the internet or to third-party integration systems.

The Philips advisory recommends configuring the environment per the D000763414 – Vue_PACS_12_Ports_Protocols_Services_Guide, which restricts network exposure of services. This guides administrators in closing unnecessary ports and reducing the attack surface while awaiting the official patch.

Insufficient technical detail is available to enumerate specific vulnerable functions, endpoints, or exact trigger conditions. The vulnerability is classified as systemic (CWE-710), which places it in a class of weaknesses that may be cumulative or multiplicative — meaning the coding-standard failure could create multiple discrete vulnerabilities across the platform's components.

Exploitation Scenarios

Since no public PoC exists and the NVD description lacks specific technical details, the attack chain is inferred from the vulnerability class (CWE-710) and the product's role in hospital infrastructure.

Step 1 — Reconnaissance/Target Identification An attacker targeting a healthcare network would identify Vue PACS servers via network scanning. PACS systems typically listen on well-known ports (e.g., DICOM on port 11112, HTTPS on 443) and may respond with identifiable banners or service fingerprints. Shodan dorks such as "Philips Vue PACS" or "Vue PACS 12" can expose internet-facing instances. In hospital networks, lateral movement from compromised workstations to PACS servers is a common path.

Step 2 — Triggering the Flaw Class The attacker would attempt to interact with the PACS server's available services, sending crafted requests designed to trigger one or more weaknesses introduced by improper coding standards. Given the CWE-710 classification, plausible triggers include: malformed DICOM files (for input validation defects), oversized network packets (for boundary-checking defects), or specially crafted authentication requests (for cryptographic or session-handling defects). The precise trigger mechanism depends on the unpatched code path.

Step 3 — Payload/Execution at Vulnerability-Class Level The attacker would deliver a payload appropriate to the specific underlying weakness — for example: a malformed DICOM image designed to exploit a buffer overflow, or a crafted HTTP request targeting an SQL injection in the web-interface component. The intent is to achieve code execution on the server, bypass authentication, or extract data from the underlying database or file system.

Step 4 — Post-Exploitation Impact Successful exploitation on a PACS server yields the attacker access to: (a) medical imaging archives (all DICOM studies for the facility), (b) the patient demographic database (name, birth date, medical record number), and (c) the radiology reading workflow. This enables patient-data exfiltration, ransomware deployment, or tampering with imaging studies to manipulate clinical decisions. Because PACS integrates with the hospital's Active Directory and other clinical systems, the compromised server can serve as a pivot point for deeper network intrusion.

No public PoC is available; the attack chain is inferred from the vulnerability class. The systemic nature of CWE-710 means the actual exploitation path is contingent upon the specific resultant weaknesses present in the deployed version.

Impact Assessment

Confidentiality Impact (High) — A successful exploit can expose protected health information (PHI): radiology images, radiology reports, and patient demographics. PHI exfiltration triggers HIPAA/HITECH breach-notification obligations and may incur regulatory fines (OCR penalties up to $1.5M per violation tier).

Integrity Impact (High) — Attackers could alter or delete imaging studies, corrupt diagnostic data, or modify reporting pipelines. Uncorrected image manipulation could negatively influence clinical decision-making and patient treatment paths.

Availability Impact (High) — Ransomware or destructive attacks on the PACS server would halt the facility's diagnostic imaging workflow, forcing manual processes and potentially delaying urgent care.

Affected Systems Scope — All Philips Vue PACS deployments running 12.2.x.x are affected. The blast radius extends to:

• The PACS server itself (database, file store, web applications)
• Connected clinical workstations (radiologist reading stations)
• Integrated systems (HIS, RIS, EHR platforms) via the PACS API
• Backup/archive infrastructure

CVSS Context — The 7.5 rating reflects high impacts across all three dimensions. The attack vector is network-based with low complexity; however, user interaction is required, suggesting that some exploitation paths involve a user action (e.g., opening a malicious file), which tempers the severity ceiling. The CVSS score does not encode the additional healthcare-sector risk that elevates business impact beyond the numeric rating.

Detection Guidance

Sigma Rule

title: Suspicious PACS Network Access Patterns
id: 4f67a52e-8a19-4b4f-95f1-2f4b8f3a75be
status: experimental
description: Detects unusual connection attempts to Philips Vue PACS services, potentially indicating exploitation of CVE-2021-27501
author: Valtersit Research
date: 2024/05/10
tags:
    - attack.t1190
    - attack.initial_access
    - cve.2021-27501
logsource:
    category: network_connection
    product: windows
detection:
    selection:
        DestinationPort:
            - 11112  # DICOM
            - 443    # HTTPS
            - 8080   # HTTP alt
        Initiated: 'true'
    filter_human:
        User|startswith:
            - 'svc_pacs'
            - 'pacs_service'
    condition: selection and not filter_human
level: medium
falsepositives:
    - Legitimate remote radiologist reading stations

YARA Rule

rule CVE_2021_27501_Philips_VuePACS_Payloads
{
    meta:
        author = "Valtersit Research"
        description = "Detects payload patterns potentially targeting CVE-2021-27501"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2021-27501"
        date = "2024-05-10"
    strings:
        $dicom_magic = { 44 49 43 4D }  // "DICM" DICOM header
        $pacs_path = /\/v1\/studies\/|\/pacs\/|\/archive\//
        $bad_cmd   = /(system|exec|spawn|popen|cmd)\s*[\(\[\{\s]/
        $sqli      = /('|\")\s*(OR|AND)\s*['\"]?\d+['\"]?\s*=\s*(['\"]?\d+|['\"]?\w+)/i
        $crypto    = /(AES|RSA|3DES|MD5|SHA1)\s*\([^)]{0,100}\)/i
    condition:
        uint32(0) == 0x4D434944  // "DICM" at file offset 128
        and ($dicom_magic or $pacs_path) and 2 of ($bad_cmd, $sqli, $crypto)
}

Suricata IDS Rule

alert tcp any any -> any 11112,443,8080 (msg:"ET EXPLOIT Philips Vue PACS CVE-2021-27501 attempted scan"; flow:to_server,established; content:"DICM"; offset:128; depth:4; content:"PACS"; nocase; distance:0; within:50; sid:202127501; rev:1; classtype:attempted-admin; reference:cve,2021-27501;)

Elastic Detection

network where process == "pacsd" or process == "vue_pacs" 
 and destination.port in (11112, 443, 8080)
 and network.direction == "ingress"
 and source.ip not in ("10.0.0.0/8", "172.16.0.0/12", "192.168.0.0/16")
 and flow == "connection"
 and event.action in ("connection_attempt", "connection_established")

Splunk SPL Query

index=network sourcetype=netflow OR sourcetype=cisco:netflow OR sourcetype=bro:conn
| search (dest_port=11112 OR dest_port=443 OR dest_port=8080) AND src_ip!=10.0.0.0/8 AND src_ip!=172.16.0.0/12 AND src_ip!=192.168.0.0/16
| where dest_ip="*pacs*" OR dest_host="*pacs*"
| stats count min(_time) max(_time) by src_ip, dest_ip, dest_port
| where count > 20
| sort - count

Wazuh OSSEC Rule

<group name="pacs,">
  <rule id="100275" level="10">
    <decoded_as>json</decoded_as>
    <field name="port">11112|443|8080</field>
    <field name="srcip">!10.0.0.0/8|!172.16.0.0/12|!192.168.0.0/16</field>
    <description>Philips Vue PACS unexpected connection attempt - CVE-2021-27501</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>exploit,pacs,</group>
  </rule>
</group>

Mitigation & Patch Guidance

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

1. Immediate Mitigations

• Apply the configuration guidance in D000763414 – Vue_PACS_12_Ports_Protocols_Services_Guide available on the Philips Incenter portal. This involves restricting the PACS server network exposure:
  • Close or disable all unnecessary ports and protocols
  • Restrict the DICOM service to only authorized clinical workstations
  • Place PACS behind a firewall with strict ACLs preventing internet exposure
• Segment the PACS server from the general hospital network; do not expose it to untrusted network segments
• Require VPN or remote-access gateway for any off-site access to the PACS

2. Patch/Upgrade Steps

• Philips will release Version 15 in Q1/2022 to remediate this issue for the Speech, MyVue, and PACS components
• Contact your Philips Sales representative or submit a quote request in the eService portal at https://eservice.philips.com to determine eligibility (releases subject to country-specific regulations)
• Validate the patch in a test environment before deployment to production
• Confirm patch integrity via signed checksum before installation on medical equipment

3. Long-Term Hardening

• Adopt a formal risk-management framework aligned with FDA/ISO 14971 for medical device security
• Establish a vendor-management program requiring Philips to disclose secure-development-lifecycle (SDL) compliance evidence
• Implement a regular patching cadence for PACS infrastructure aligned with Philips security advisories
• Enforce multi-factor authentication (MFA) for all administrative access to PACS
• Deploy network intrusion detection and host-based monitoring solutions to establish an early-warning capability
• Conduct annual penetration tests of the PACS environment to identify configuration gaps

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2021-27501
2. Philips Product Security Advisory: https://www.philips.com/a-w/security/security-advisories.html (search for CVE-2021-27501)
3. CISA ICS Medical Advisory (where applicable): https://www.cisa.gov/ics/advisories/icsma-XX-XXX-XX (Philips Vue PACS)
4. MITRE ATT&CK Technique: https://attack.mitre.org/techniques/T1190/
5. Philips eService Portal: https://eservice.philips.com (for patch eligibility and download)

Threat-Actor Intelligence: No known threat-actor campaigns specifically targeting CVE-2021-27501 have been documented. The EPSS score of 0.00910 (56.8th percentile) indicates a moderate likelihood of exploitation in the wild relative to all known CVEs. The vulnerability is NOT listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, meaning there is no confirmed exploitation activity at the time of this report. However, the healthcare sector remains a persistently targeted vertical for ransomware groups, and PACS systems have been leveraged in prior attacks (e.g., Ryuk/Conti campaigns targeting hospitals), so exploit development against this class of weakness should be considered plausible.