CVE-2021-33020

Executive Summary

CVE-2021-33020 affects Philips Vue PACS versions 12.2.x.x and prior, a medical imaging platform used to store, retrieve, and display radiological studies. The vulnerability stems from the product's continued use of a cryptographic key or password beyond its designated expiration date, which significantly weakens the confidentiality and integrity guarantees of the system by providing an extended time window for offline cracking or exhaustive search attacks against the key material.

With a CVSS score of 8.2 (High), the flaw is particularly concerning in a healthcare environment where patient data (protected health information) and diagnostic imaging integrity are at stake. Philips addressed the issue in Vue Motion version 12.2.1.5, released in June 2020, and provided configuration guidance via the referenced ports/protocols/services guide. However, patch confidence is rated 2/4 — the fix is claimed by a single source and is not independently confirmed. No public exploit, PoC, or CISA KEV listing exists, and EPSS probability is low (0.00617), indicating limited observed exploitation activity in the wild.

Technical Analysis

The NVD description states that "Philips Vue PACS versions 12.2.x.x and prior uses a cryptographic key or password past its expiration date, which diminishes its safety significantly by increasing the timing window for cracking attacks against that key."

Vulnerability Mechanism. The core issue is a lifecycle-management failure of cryptographic material. Cryptographic best practice mandates that encryption keys and authentication passwords be rotated at defined intervals (e.g., 90 days for passwords, yearly for asymmetric keys). When a key or password exceeds its cryptographic period of use, the following risks materialize:

1. Extended Cracking Window: For symmetric keys or passwords derived via key-derivation functions, an attacker who obtains a ciphertext or password hash can run offline brute-force attacks. The longer the credential remains valid, the more compute time the attacker has. The timing window grows from weeks to years, dramatically increasing the probability of successful key recovery.
2. Key Compromise Undetected: Expired keys are often excluded from audit/monitoring processes. A compromised key that should have been rotated may go unnoticed, and the exposure window extends indefinitely.
3. Increased Likelihood of Exposure During Transition: Legacy keys are sometimes left in code, configuration files, or backups. When the expiration date passes without rotation, those artifacts remain exploitable.

Attack Surface. Vue PACS is a picture archiving and communication system — a network-centric suite deployed across hospitals and clinics. Typical components include:

• Image acquisition modalities (CT, MRI, X-ray) that send DICOM studies to the archive.
• A central archive server storing images and metadata.
• Workstation clients used by radiologists to view studies.
• Possibly a web-based viewer (Vue Motion) for remote access.

The vulnerable key or password may be used in several contexts: TLS certificate private keys, DICOM node authentication credentials, database connection strings, or service account passwords. If any of these are expired-but-in-use, an attacker who has already achieved a foothold (or who intercepts network traffic) can mount offline attacks against captured key material.

Code-Level Details. The NVD description provides no function names, API endpoints, or file paths. Insufficient technical detail is available to specify exactly which component maintains the expired key or what algorithm is in use. The vulnerability class, however, is clearly mapped to CWE-798 (Use of Hard-coded Credentials) or CWE-324 (Use of a Key Past its Expiration Date). The absence of granular details means detection must rely on behavioral indicators rather than signature matching.

Exploitation Scenarios

No public PoC or exploit code is available for CVE-2021-33020. The following attack chain is inferred from the vulnerability class and the deployment context of Philips Vue PACS. It should be treated as a plausible scenario, not a documented exploit path.

Step 1 — Reconnaissance and Target Identification. An attacker identifies a hospital or imaging center running Philips Vue PACS. Shodan queries such as product:"Philips Vue PACS" or scans for DICOM port 11112 (default DICOM) and web interfaces for Vue Motion (commonly on ports 443/8443) can reveal exposed instances. Banner grabbing on these ports may reveal version banners containing "Vue PACS 12.x" allowing the attacker to confirm the vulnerable version range.

Step 2 — Triggering the Vulnerability-Class Condition. The attacker obtains key material or a password hash. Vectors for this acquisition:

• Network sniffing: If the expired key is used for TLS, the attacker can perform a man-in-the-middle attack. A valid certificate chain with a long-lived key that the attacker already captured (e.g., from a prior breach) becomes usable indefinitely because it is past rotation.
• Response to known plaintext: For encrypted DICOM traffic, an attacker with access to both ciphertext and known plaintext (e.g., standard DICOM headers) can perform offline key-recovery attacks.
• Hash capture: If the expired password is used for web authentication (Vue Motion), the attacker may capture an HTTP Digest/MD5 hash or an NTLM-style hash via network interception.

Step 3 — Exploitation / Key Recovery. The attacker runs offline brute-force or dictionary attacks against the captured material. Because the key has been in use beyond its expiration date, the attacker benefits from an extended time window — potentially months or years — to run specialized cracking hardware (GPUs) or distributed cracking clusters. The specific algorithm (AES, RSA, bcrypt, SHA-256) is not documented, so the attack complexity varies.

Step 4 — Post-Exploitation Impact. Upon key/password recovery, the attacker can:

• Decrypt intercepted DICOM studies, exposing patient PHI and radiology images.
• Authenticate as a legitimate system component (e.g., an imaging modality or a workstation), enabling the injection of forged DICOM studies or the tampering of existing images — a severe integrity threat because clinicians make diagnostic decisions based on these images.
• Move laterally from the PACS to the hospital network, as PACS systems often share trust relationships with Active Directory and other clinical systems.

Impact Assessment

Business Impact. A compromise of Vue PACS directly threatens patient safety and privacy. Altered radiology images could lead to misdiagnosis or incorrect treatment planning. Exposure of PHI triggers regulatory obligations under HIPAA (US), GDPR (EU), and various national health-data laws, potentially incurring fines, litigation, and reputational damage.

Affected Systems. All Philips Vue PACS deployments running versions 12.2.x.x and prior. This includes the central archive server, Vue Motion client, and any system relying on the shared cryptographic material.

Blast Radius. The CVSS score of 8.2 reflects the following (inferred) sub-scores:

• Attack Vector: Network — the vulnerable key is part of a network-accessible system.
• Attack Complexity: Low — offline cracking does not require special conditions beyond key capture.
• Privileges Required: None — obtaining the key material may not require prior authentication (e.g., via sniffing).
• User Interaction: None.
• Confidentiality Impact: High — full exposure of patient imaging data.
• Integrity Impact: Low — while image tampering is possible, it would require deliberate effort.
• Availability Impact: Low — the vulnerability does not directly enable DoS.

Threat Landscape. EPSS score of 0.00617 indicates a low probability of exploitation in the wild. CISA KEV does not list this CVE, and no threat-actor campaigns have been publicly attributed. Nevertheless, healthcare-targeting ransomware groups (e.g., Ryuk, Conti) routinely scan for exposed medical infrastructure; the cryptographic weakness is a plausible secondary vector in such campaigns.

Detection Guidance

The following detection rules focus on behavioral anomalies rather than exploit signatures, given the absence of a documented attack pattern. They center on: (1) abnormal network traffic to/from PACS on non-standard ports, (2) unexpected DICOM traffic decryption attempts, and (3) authentication anomalies on Vue Motion.

Sigma Rule

title: Suspicious Authentication Attempts on Philips Vue PACS
id: 0b8e4a97-0a2a-4ca1-9a8e-4dc6a1b99d12
status: experimental
description: Detects high-volume or repeated authentication failures against Vue PACS that may indicate offline cracking or credential stuffing.
logsource:
  category: application
  product: philips_vue_pacs
detection:
  selection:
    event_type: authentication_failure
    user: "%"
    source_ip:
      - "10.%"
      - "172.16.%"
      - "192.168.%"
  timeframe: 5m
  condition: selection | count(user) > 50
level: medium
tags:
  - attack.t1110
  - attack.t1190

YARA Rule

rule Philips_Vue_PACS_Expired_Key_Indicators
{
    meta:
        author = "Threat Intel Team"
        description = "Detects files referencing long-expired key timestamps or cryptographic parameters flagged in Vue PACS configurations"
        date = "2021-06-01"
    strings:
        $s1 = "expired" ascii nocase
        $s2 = "certificate not valid" ascii nocase
        $s3 = "key rotation" ascii nocase
        $s4 = "12.2.1" ascii nocase
        $s5 = "Philips" ascii nocase
    condition:
        all of them and filesize < 2MB
}

Suricata IDS Rule

alert tcp any any -> $HOSPITAL_NET 11112 (msg:"CVE-2021-33020 Philips Vue PACS - Unusual DICOM Traffic"; flow:to_server; dsize:>1000; content:"|01 00|"; depth:2; threshold:type both, track by_src, count 100, seconds 60; classtype:attempted-admin; sid:20213301; rev:1;)

Elastic Detection

any where process.name == "vuepacs.exe" and (
  network.protocol == "dicom" and network.direction == "egress"
) or (
  network.protocol == "tls" and network.destination.port == 443 and
  network.direction == "egress" and
  process.name == "vueviewer.exe"
)

Splunk SPL Query

index=vuepacs sourcetype=authentication
| where LIKE(action, "%fail%")
| bin _time span=1m as minute
| stats count by minute, src_ip, user
| where count > 20
| table _time, src_ip, user, count

Wazuh OSSEC Rule

<group name="philips_vue_pacs,">
  <rule id="100330" level="10">
    <decoded_as>json</decoded_as>
    <field name="type">auth_failure</field>
    <description>CVE-2021-33020: Repeated authentication failures on Philips Vue PACS</description>
    <group>authentication_failures,</group>
    <if_sid>100329</if_sid>
    <frequency>10</frequency>
    <timeframe>120</timeframe>
    <same_source_ip />
  </rule>
</group>

Mitigation & Patch Guidance

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

1. Immediate Mitigations

• Restrict network access to Vue PACS systems: place behind a firewall; whitelist only known modality and workstation IPs on DICOM port 11112.
• Disable or restrict remote web access to Vue Motion unless protected by VPN or zero-trust proxy.
• Monitor authentication logs and DICOM traffic for anomalies.
• If the expired key is suspected to be a TLS certificate, replace it immediately, even before a full upgrade.

2. Patch/Upgrade Steps

• Philips recommends configuring the Vue PACS environment per document D000763414 – Vue_PACS_12_Ports_Protocols_Services_Guide (available on Incenter).
• Philips released Version 12.2.1.5 in June 2020 for Vue Motion to remediate this issue. Contact Philips support to obtain and schedule the upgrade.
• Reach out to your Philips Sales representative or submit a request via the eService portal (https://eservice.philips.com) for:
  • Applicable version updates for the full PACS suite.
  • Confirmation of whether the fix extends beyond Vue Motion to all Vue PACS components.
• Note: release availability is subject to country-specific regulatory approvals.

3. Long-Term Hardening

• Establish a formal cryptographic key-rotation policy (e.g., TLS keys every 12 months, service-account passwords every 90 days).
• Inventory all keys/certificates across the PACS environment; ensure no key exceeds its validity period.
• Segment the clinical network (DICOM traffic) from general IT traffic.
• Implement centralized logging and SIEM monitoring for all PACS components.
• Conduct periodic audits of vendor advisories from Philips’ product security page.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2021-33020
2. Philips Product Security Advisories: https://www.usa.philips.com/healthcare/about/cyber-security/advisories
3. Philips eService Portal: https://eservice.philips.com
4. CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (CVE-2021-33020 not listed)
5. Philips Incenter (for D000763414 guide): https://www.incenter.philips.com

No threat-actor campaigns or exploit-in-the-wild evidence were publicly documented for CVE-2021-33020 as of the assessment date. Organizations should nonetheless treat the healthcare-manufacturing sector as a persistent target for ransomware and data-exfiltration groups, and apply the above mitigations regardless.