CVE-2021-33018

Executive Summary

CVE-2021-33018 is a cryptographic weakness in Philips Vue PACS (Picture Archiving and Communication System) versions 12.2.x.x and earlier, arising from the use of a broken or risky cryptographic algorithm. The vulnerability is rated 7.5 (High) on the CVSS scale and exposes sensitive medical imaging data to potential unauthorized access. Healthcare organizations running affected versions of Vue PACS — particularly those with internet-exposed or poorly segmented deployments — are at risk of data confidentiality loss involving protected health information (PHI).

Technical Analysis

The vulnerability is classified under CWE-327 (Use of a Broken or Risky Cryptographic Algorithm). Philips Vue PACS versions 12.2.x.x and prior employ cryptographic mechanisms that are considered cryptographically weak or deprecated. Specific algorithm details (e.g., whether the issue involves SSLv3, RC4, MD5, or insufficient key lengths) are not disclosed in the NVD description or the CNA advisory available at the time of this writing. The Philips advisory does not enumerate the exact algorithm(s) flagged, nor does it specify which communication channels (e.g., web console, DICOM TLS endpoints, database connections) are affected.

From a technical standpoint, the failure mode is as follows:

• Vulnerability mechanism: The affected system uses a cryptographic algorithm (or protocol) that has known weaknesses, meaning the cipher can be broken with realistic attacker resources (e.g., via offline brute force, frequency analysis, or man-in-the-middle decryption).
• Attack surface: Any network-facing service in Vue PACS that relies on the broken crypto — including, potentially, HTTPS administration interfaces, DICOM traffic, or inter-service authentication channels. The attack requires the attacker to intercept or capture ciphertext (passive attack) or to impersonate a legitimate peer (active man-in-the-middle).
• Confidentiality impact: The NVD description explicitly states the risk of "exposure of sensitive information." This implies the flaw primarily compromises data confidentiality rather than integrity or availability, consistent with the CVSS subscores (C:H/I:N/A:N per the derived vector).

Because the specific algorithm and affected component are not enumerated in available technical data, further code-level analysis is not possible without vendor documentation. It is recommended that security teams request the Philips advisory from the Philips Product Security website for algorithm-level specifics.

Exploitation Scenarios

No public PoC or exploit code exists for CVE-2021-33018 at the time of writing. The attack chain is inferred from the vulnerability class (broken/risky crypto) and the device's role in medical imaging.

Scenario 1 — Passive Network Decryption (Man-in-the-Middle)

1. Reconnaissance: An attacker with network access (either on the internal hospital network or via an exposed service) scans for Vue PACS hosts using Shodan or internal scanning. Target identification is aided by default ports used by PACS systems (e.g., DICOM port 11112, HTTPS on 443, or SQL ports) and by product banners.
2. Trigger: The attacker positions themselves between the client (e.g., a radiologist workstation) and the Vue PACS server — via ARP spoofing, rogue Wi-Fi, or compromised network equipment.
3. Payload/Execution: No payload is injected. The attacker passively captures the TLS/SSL handshake and subsequent encrypted traffic. Because the algorithm is broken (e.g., weak key exchange or stream cipher weakness), the attacker performs offline cryptanalysis to recover the session key or plaintext.
4. Post-Exploitation Impact: The attacker obtains medical images (X-rays, MRIs, CT scans) and associated patient metadata (names, dates of birth, medical record numbers). Data can be sold, used for blackmail, or leveraged for insurance fraud. Confidentiality is fully compromised.

Scenario 2 — Direct Decryption of Captured DICOM Data

1. Reconnaissance: Attacker obtains network packet captures (pcap) of DICOM traffic from a breached network segment or via physical access to storage media.
2. Trigger: The attacker analyzes the captured ciphertext offline, exploiting the known weakness in the algorithm to recover plaintext without interacting with the live system.
3. Payload/Execution: No active exploitation is required — purely cryptographic attack against captured data.
4. Post-Exploitation Impact: Bulk extraction of historical imaging data, leading to mass PHI exposure.

Note: No public PoC available; attack chain is inferred from vulnerability class.

Impact Assessment

• CVSS Score: 7.5 (High) with the derived vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N — the attack is network-based, requires no privileges, and can be executed without user interaction. The primary effect is a High confidentiality impact with no integrity or availability impact.
• Business Impact: For healthcare delivery organizations, this vulnerability threatens compliance with HIPAA, GDPR, and other data protection regulations. A breach of imaging data could result in fines up to $50,000 per record (HIPAA OCR), reputational damage, and potential class-action lawsuits.
• Affected Systems: All Philips Vue PACS deployments running version 12.2.x.x and prior. Given that PACS systems are mission-critical for radiology departments, patching windows must be coordinated carefully with clinical operations.
• Blast Radius: If the affected service is reachable from the internet, the attack surface is global. However, even on internal networks, a low-privilege user (e.g., a compromised workstation) could pivot to intercept PACS traffic.

Detection Guidance

Sigma Rule

title: Detects Weak Cipher Suites on Philips Vue PACS
id: 47e51d99-0f9a-4f5e-9d5f-123456789abc
status: experimental
description: Detects TLS handshakes using known-broken cipher suites (e.g., RC4, 3DES, NULL ciphers) targeting Philips Vue PACS hosts.
author: Valtersit Threat Intel
date: 2023/10/01
logsource:
  category: network-connection
  product: zeek
detection:
  selection:
    server.certificate.issuer|contains: "Philips"  # Adjust based on cert naming
    tls.ciphers|contains:
      - "RC4"
      - "TLS_RSA_WITH_3DES_EDE_CBC_SHA"
      - "TLS_RSA_WITH_RC4_128_SHA"
      - "TLS_ECDHE_RSA_WITH_RC4_128_SHA"
      - "TLS_RSA_WITH_NULL_SHA"
  condition: selection
level: high
falsepositives:
  - Legacy clients that cannot upgrade to modern protocols
tags:
  - attack.t1190
  - attack.collection

YARA Rule

rule Philips_Vue_PACS_Broken_Crypto_Config
{
    meta:
        author = "Valtersit Threat Intel"
        description = "Detects configuration files or logs referencing deprecated crypto algorithms in Philips Vue PACS"
        date = "2023-10-01"
        cve = "CVE-2021-33018"
        severity = "high"
    strings:
        $s1 = "RC4" ascii wide
        $s2 = "3DES" ascii wide
        $s3 = "SSLv3" ascii wide
        $s4 = "TLS_RSA_WITH_RC4_128_SHA" ascii wide
        $s5 = "Vue PACS" ascii wide
        $s6 = "VuePACS" ascii wide
    condition:
        any of ($s1, $s2, $s3, $s4) and any of ($s5, $s6)
}

Suricata IDS Rule

alert tls any any -> any any (msg:"CVE-2021-33018 - Philips Vue PACS weak cipher suite detected"; ciphers:"RC4,3DES"; flow:to_server; tls.version:<=0x0302; classtype:policy-violation; sid:202133018; rev:1;)

Elastic Detection

sequence by host.id with maxspan=5m
  [network where
     destination.port in (443, 11112) and
     destination.ip == "PHILIPS_VUE_PACS_IP" and  // Substitute with asset IP
     network.protocol == "tls" and
     tls.cipher in ("RC4-SHA", "DES-CBC3-SHA", "NULL-SHA256")
  ]

Splunk SPL Query

index=netflow OR index=netfw sourcetype=pan:traffic OR sourcetype=cisco:esa
| search dest_port IN (443, 11112) 
| eval cipher_lower=lower(cipher)
| where match(cipher_lower, "rc4|3des|des-cbc3|null-sha")
| stats count by src_ip, dest_ip, dest_port, cipher
| where count > 5

Wazuh OSSEC Rule

<group name="philips_vue_pacs">
  <rule id="856070" level="12">
    <decoded_as>json</decoded_as>
    <field name="event.category">network</field>
    <field name="tls.cipher">RC4|3DES|NULL_SHA</field>
    <field name="destination.service">pacs|whitelist service</field>
    <description>Philips Vue PACS - Weak cryptographic algorithm detected in TLS handshake (CVE-2021-33018)</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>cve-2021-33018</group>
  </rule>
</group>

Mitigation & Patch Guidance

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

Immediate Mitigations (until patch is applied):

1. Network Segmentation: Restrict access to Vue PACS systems to trusted clinical subnets only. Disable direct internet exposure via firewall rules.
2. Disable Weak Ciphers: If the administrative interface (e.g., web console) is running on a front-end web server (e.g., IIS or Apache reverse proxy), disable RC4, 3DES, and TLS 1.0/1.1 at the proxy level.
3. VPN / Tunneling: Require all remote access to Vue PACS to use a modern VPN with strong crypto (TLS 1.2/1.3, AES-GCM).
4. Network Monitoring: Enable TLS inspection (where feasible) and alert on any cipher suites matching the weak set.

Patch / Upgrade:

• Philips has announced that Version 15 (released Q1/2022) remediates this issue for both Speech and PACS components. Contact Philips support for deployment scheduling.
• Review the Philips advisory (available on the Philips Product Security website) for the specific list of affected algorithms and any interim hotfixes.
• Follow guidance in D000763414 – Vue_PACS_12_Ports_Protocols_Services_Guide (available on Incenter) to configure ports and protocols securely.

Long-Term Hardening:

• Enforce TLS 1.2+ with AES-GCM or ChaCha20-Poly1305 cipher suites across all PACS components.
• Implement mutual TLS (mTLS) where supported to mitigate MITM attacks.
• Regularly monitor Philips security advisories and the CISA KEV catalog (note: CVE-2021-33018 is not currently listed on KEV).
• Perform periodic cryptographic configuration audits (e.g., using nmap --script ssl-enum-ciphers or testssl.sh) on all clinical systems.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2021-33018
2. Philips Product Security Advisory: https://www.philips.com/a-w/security/security-advisories.html
3. CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (CVE-2021-33018 listed as NOT on KEV)
4. CWE-327 Reference: https://cwe.mitre.org/data/definitions/327.html
5. Philips eService Portal (patch/update requests): https://incenter.medical.philips.com

Threat Actor / Exploit Activity: No public exploit code, PoC, or known in-the-wild exploitation campaigns have been identified for CVE-2021-33018. EPSS score (0.00554, 43.4th percentile) indicates very low likelihood of active exploitation. However, historical targeting of medical devices (e.g., Ryuk/Conti campaigns against hospital infrastructure) highlights the risk of patient-data impact once any PoC emerges.