CVE-2021-21004 Vulnerability Analysis & Exploit Details

CVE-2021-21004
Vulnerability Scoring

7.4
/10
Very High Risk

Highly exploitable, CVE-2021-21004 poses a critical security risk that could lead to severe breaches.

Attack Complexity Details

  • Attack Complexity: Low
    Exploits can be performed without significant complexity or special conditions.
  • Attack Vector: Adjacent_network
    Attack Vector Under Analysis
  • Privileges Required: None
    No privileges are required for exploitation.
  • Scope: Changed
    Successful exploitation can impact components beyond the vulnerable component.
  • User Interaction: Required
    User interaction is necessary for successful exploitation.

CVE-2021-21004 Details

Status: Modified

Last updated: 🕠 21 Nov 2024, 05:47 UTC
Originally published on: 🕖 25 Jun 2021, 19:15 UTC

Time between publication and last update: 1244 days

CVSS Release: version 3

CVSS3 Source

info@cert.vde.com

CVSS3 Type

Secondary

CVSS3 Vector

CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:N

CVE-2021-21004 Vulnerability Summary

CVE-2021-21004: In Phoenix Contact FL SWITCH SMCS series products in multiple versions an attacker may insert malicious code via LLDP frames into the web-based management which could then be executed by the client.

Assessing the Risk of CVE-2021-21004

Access Complexity Graph

The exploitability of CVE-2021-21004 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).

Exploitability Analysis for CVE-2021-21004

With low attack complexity and no required privileges, CVE-2021-21004 is an easy target for cybercriminals. Organizations should prioritize immediate mitigation measures to prevent unauthorized access and data breaches.

Understanding AC and PR

A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.

Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.

Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.

CVSS Score Breakdown Chart

Above is the CVSS Sub-score Breakdown for CVE-2021-21004, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.

CIA Impact Analysis

Below is the Impact Analysis for CVE-2021-21004, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.

  • Confidentiality: Low
    CVE-2021-21004 could lead to minor leaks of non-critical information without major privacy breaches.
  • Integrity: High
    CVE-2021-21004 could allow unauthorized modifications to data, potentially affecting system reliability and trust.
  • Availability: None
    CVE-2021-21004 does not impact system availability.

Exploit Prediction Scoring System (EPSS)

The EPSS score estimates the probability that this vulnerability will be exploited in the near future.

EPSS Score: 0.062% (probability of exploit)

EPSS Percentile: 29.45% (lower percentile = lower relative risk)
This vulnerability is less risky than approximately 70.55% of others.

CVE-2021-21004 References

External References

CWE Common Weakness Enumeration

CWE-79

CAPEC Common Attack Pattern Enumeration and Classification

  • XSS Using MIME Type Mismatch CAPEC-209 An adversary creates a file with scripting content but where the specified MIME type of the file is such that scripting is not expected. The adversary tricks the victim into accessing a URL that responds with the script file. Some browsers will detect that the specified MIME type of the file does not match the actual type of its content and will automatically switch to using an interpreter for the real content type. If the browser does not invoke script filters before doing this, the adversary's script may run on the target unsanitized, possibly revealing the victim's cookies or executing arbitrary script in their browser.
  • DOM-Based XSS CAPEC-588 This type of attack is a form of Cross-Site Scripting (XSS) where a malicious script is inserted into the client-side HTML being parsed by a web browser. Content served by a vulnerable web application includes script code used to manipulate the Document Object Model (DOM). This script code either does not properly validate input, or does not perform proper output encoding, thus creating an opportunity for an adversary to inject a malicious script launch a XSS attack. A key distinction between other XSS attacks and DOM-based attacks is that in other XSS attacks, the malicious script runs when the vulnerable web page is initially loaded, while a DOM-based attack executes sometime after the page loads. Another distinction of DOM-based attacks is that in some cases, the malicious script is never sent to the vulnerable web server at all. An attack like this is guaranteed to bypass any server-side filtering attempts to protect users.
  • Reflected XSS CAPEC-591 This type of attack is a form of Cross-Site Scripting (XSS) where a malicious script is "reflected" off a vulnerable web application and then executed by a victim's browser. The process starts with an adversary delivering a malicious script to a victim and convincing the victim to send the script to the vulnerable web application.
  • Stored XSS CAPEC-592 An adversary utilizes a form of Cross-site Scripting (XSS) where a malicious script is persistently "stored" within the data storage of a vulnerable web application as valid input.
  • Cross-Site Scripting (XSS) CAPEC-63 An adversary embeds malicious scripts in content that will be served to web browsers. The goal of the attack is for the target software, the client-side browser, to execute the script with the users' privilege level. An attack of this type exploits a programs' vulnerabilities that are brought on by allowing remote hosts to execute code and scripts. Web browsers, for example, have some simple security controls in place, but if a remote attacker is allowed to execute scripts (through injecting them in to user-generated content like bulletin boards) then these controls may be bypassed. Further, these attacks are very difficult for an end user to detect.
  • AJAX Footprinting CAPEC-85 This attack utilizes the frequent client-server roundtrips in Ajax conversation to scan a system. While Ajax does not open up new vulnerabilities per se, it does optimize them from an attacker point of view. A common first step for an attacker is to footprint the target environment to understand what attacks will work. Since footprinting relies on enumeration, the conversational pattern of rapid, multiple requests and responses that are typical in Ajax applications enable an attacker to look for many vulnerabilities, well-known ports, network locations and so on. The knowledge gained through Ajax fingerprinting can be used to support other attacks, such as XSS.

Vulnerable Configurations

  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_16tx_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_16tx_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_16tx_firmware:4.70:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_16tx_firmware:4.70:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_switch_smcs_16tx:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_switch_smcs_16tx:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_14tx\/2fx_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_14tx\/2fx_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_14tx\/2fx_firmware:4.70:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_14tx\/2fx_firmware:4.70:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_switch_smcs_14tx\/2fx:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_switch_smcs_14tx\/2fx:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_14tx\/2fx-sm_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_14tx\/2fx-sm_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_14tx\/2fx-sm_firmware:4.70:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_14tx\/2fx-sm_firmware:4.70:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_switch_smcs_14tx\/2fx-sm:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_switch_smcs_14tx\/2fx-sm:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_8gt_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_8gt_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_8gt_firmware:4.70:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_8gt_firmware:4.70:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_switch_smcs_8gt:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_switch_smcs_8gt:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_6gt\/2sfp_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_6gt\/2sfp_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_6gt\/2sfp_firmware:4.70:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_6gt\/2sfp_firmware:4.70:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_switch_smcs_6gt\/2sfp:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_switch_smcs_6gt\/2sfp:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_8tx-pn_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_8tx-pn_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_8tx-pn_firmware:4.70:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_8tx-pn_firmware:4.70:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_switch_smcs_8tx-pn:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_switch_smcs_8tx-pn:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_4tx-pn_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_4tx-pn_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_4tx-pn_firmware:4.70:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_4tx-pn_firmware:4.70:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_switch_smcs_4tx-pn:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_switch_smcs_4tx-pn:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_8tx_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_8tx_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_8tx_firmware:4.70:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_8tx_firmware:4.70:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_switch_smcs_8tx:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_switch_smcs_8tx:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_6tx\/2sfp_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_6tx\/2sfp_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smcs_6tx\/2sfp_firmware:4.70:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smcs_6tx\/2sfp_firmware:4.70:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_switch_smcs_6tx\/2sfp:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_switch_smcs_6tx\/2sfp:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smn_6tx\/2pof-pn_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smn_6tx\/2pof-pn_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smn_6tx\/2pof-pn_firmware:4.70:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smn_6tx\/2pof-pn_firmware:4.70:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_switch_smn_6tx\/2pof-pn:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_switch_smn_6tx\/2pof-pn:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smn_8tx-pn_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smn_8tx-pn_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smn_8tx-pn_firmware:4.70:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smn_8tx-pn_firmware:4.70:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_switch_smn_8tx-pn:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_switch_smn_8tx-pn:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smn_6tx\/2fx_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smn_6tx\/2fx_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smn_6tx\/2fx_firmware:4.70:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smn_6tx\/2fx_firmware:4.70:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_switch_smn_6tx\/2fx:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_switch_smn_6tx\/2fx:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smn_6tx\/2fx_sm_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smn_6tx\/2fx_sm_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_switch_smn_6tx\/2fx_sm_firmware:4.70:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_switch_smn_6tx\/2fx_sm_firmware:4.70:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_switch_smn_6tx\/2fx_sm:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_switch_smn_6tx\/2fx_sm:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_nat_smn_8tx_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_nat_smn_8tx_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_nat_smn_8tx_firmware:4.63:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_nat_smn_8tx_firmware:4.63:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_nat_smn_8tx:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_nat_smn_8tx:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_nat_smn_8tx-m_firmware:-:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_nat_smn_8tx-m_firmware:-:*:*:*:*:*:*:*
  • cpe:2.3:o:phoenixcontact:fl_nat_smn_8tx-m_firmware:4.63:*:*:*:*:*:*:*
    cpe:2.3:o:phoenixcontact:fl_nat_smn_8tx-m_firmware:4.63:*:*:*:*:*:*:*
  • cpe:2.3:h:phoenixcontact:fl_nat_smn_8tx-m:-:*:*:*:*:*:*:*
    cpe:2.3:h:phoenixcontact:fl_nat_smn_8tx-m:-:*:*:*:*:*:*:*

Protect Your Infrastructure against CVE-2021-21004: Combat Critical CVE Threats

Stay updated with real-time CVE vulnerabilities and take action to secure your systems. Enhance your cybersecurity posture with the latest threat intelligence and mitigation techniques. Develop the skills necessary to defend against CVEs and secure critical infrastructures. Join the top cybersecurity professionals safeguarding today's infrastructures.

Other 5 Recently Published CVEs Vulnerabilities

  • CVE-2025-66026 – REDAXO is a PHP-based CMS. Prior to version 5.20.1, a reflected Cross-Site Scripting (XSS) vulnerability exists in the Mediapool view where the req...
  • CVE-2025-66025 – Caido is a web security auditing toolkit. Prior to version 0.53.0, the Markdown renderer used in Caido’s Findings page improperly handled user-supp...
  • CVE-2025-66022 – FACTION is a PenTesting Report Generation and Collaboration Framework. Prior to version 1.7.1, an extension execution path in Faction’s extension f...
  • CVE-2025-66269 – The RupsMon and USBMate services in UPSilon 2000 run with SYSTEM privileges and contain unquoted service paths. This allows a local attacker to per...
  • CVE-2025-66266 – The RupsMon.exe service executable in UPSilon 2000 has insecure permissions, allowing the 'Everyone' group Full Control. A local attacker can repla...