CVE-2021-20153 Vulnerability Analysis & Exploit Details

CVE-2021-20153
Vulnerability Scoring

6.8
/10
High Risk

If left unpatched, CVE-2021-20153 could lead to major system disruptions or data loss.

Attack Complexity Details

  • Attack Complexity: Low
    Exploits can be performed without significant complexity or special conditions.
  • Attack Vector: Physical
    Physical access is required to exploit this vulnerability.
  • Privileges Required: None
    No privileges are required for exploitation.
  • Scope: Unchanged
    Exploit remains within the originally vulnerable component.
  • User Interaction: None
    No user interaction is necessary for exploitation.

CVE-2021-20153 Details

Status: Modified

Last updated: 🕠 21 Nov 2024, 05:46 UTC
Originally published on: 🕙 30 Dec 2021, 22:15 UTC

Time between publication and last update: 1056 days

CVSS Release: version 3

CVSS3 Source

nvd@nist.gov

CVSS3 Type

Primary

CVSS3 Vector

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

CVE-2021-20153 Vulnerability Summary

CVE-2021-20153: Trendnet AC2600 TEW-827DRU version 2.08B01 contains a symlink vulnerability in the bittorrent functionality. If enabled, the bittorrent functionality is vulnerable to a symlink attack that could lead to remote code execution on the device. If an end user inserts a flash drive with a malicious symlink on it that the bittorrent client can write downloads to, then a user is able to download arbitrary files to any desired location on the devices filesystem, which could lead to remote code execution. Example directories vulnerable to this include "config", "downloads", and "torrents", though it should be noted that "downloads" is the only vector that allows for arbitrary files to be downloaded to arbitrary locations.

Assessing the Risk of CVE-2021-20153

Access Complexity Graph

The exploitability of CVE-2021-20153 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-2021-20153

With low attack complexity and no required privileges, CVE-2021-20153 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-2021-20153, 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-2021-20153, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.

  • Confidentiality: High
    Exploiting CVE-2021-20153 can result in unauthorized access to sensitive data, severely compromising data privacy.
  • Integrity: High
    CVE-2021-20153 could allow unauthorized modifications to data, potentially affecting system reliability and trust.
  • Availability: High
    CVE-2021-20153 can disrupt system operations, potentially causing complete denial of service (DoS).

Exploit Prediction Scoring System (EPSS)

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

EPSS Score: 0.165% (probability of exploit)

EPSS Percentile: 54.52% (lower percentile = lower relative risk)
This vulnerability is less risky than approximately 45.48% of others.

CVE-2021-20153 References

External References

CWE Common Weakness Enumeration

CWE-59

CAPEC Common Attack Pattern Enumeration and Classification

  • Symlink Attack CAPEC-132 An adversary positions a symbolic link in such a manner that the targeted user or application accesses the link's endpoint, assuming that it is accessing a file with the link's name.
  • Using Malicious Files CAPEC-17 An attack of this type exploits a system's configuration that allows an adversary to either directly access an executable file, for example through shell access; or in a possible worst case allows an adversary to upload a file and then execute it. Web servers, ftp servers, and message oriented middleware systems which have many integration points are particularly vulnerable, because both the programmers and the administrators must be in synch regarding the interfaces and the correct privileges for each interface.
  • Leverage Executable Code in Non-Executable Files CAPEC-35 An attack of this type exploits a system's trust in configuration and resource files. When the executable loads the resource (such as an image file or configuration file) the attacker has modified the file to either execute malicious code directly or manipulate the target process (e.g. application server) to execute based on the malicious configuration parameters. Since systems are increasingly interrelated mashing up resources from local and remote sources the possibility of this attack occurring is high.
  • Manipulating Web Input to File System Calls CAPEC-76 An attacker manipulates inputs to the target software which the target software passes to file system calls in the OS. The goal is to gain access to, and perhaps modify, areas of the file system that the target software did not intend to be accessible.

Vulnerable Configurations

  • cpe:2.3:o:trendnet:tew-827dru_firmware:2.08b01:*:*:*:*:*:*:*
    cpe:2.3:o:trendnet:tew-827dru_firmware:2.08b01:*:*:*:*:*:*:*
  • cpe:2.3:h:trendnet:tew-827dru:2.0:*:*:*:*:*:*:*
    cpe:2.3:h:trendnet:tew-827dru:2.0:*:*:*:*:*:*:*

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