Directory Traversal Affecting io.vertx:vertx-web package, versions [4.0.0,4.3.8)


Severity

0.0
medium
0
10

    Threat Intelligence

    Exploit Maturity
    Proof of concept
    EPSS
    0.14% (49th percentile)

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  • Snyk ID SNYK-JAVA-IOVERTX-3318108
  • published 10 Feb 2023
  • disclosed 10 Feb 2023
  • credit Unknown

How to fix?

Upgrade io.vertx:vertx-web to version 4.3.8 or higher.

Overview

io.vertx:vertx-web is a HTTP web applications for Vert.x.

Affected versions of this package are vulnerable to Directory Traversal when running Vertx web applications that serve files using StaticHandle. If the mount point is a wildcard (*) then an attacker can exfiltrate any class path resource.

When computing the relative path to locate the resource, in case of wildcards, the code returns the user input (without validation) as the segment to lookup. Even though checks are performed to avoid escaping the sandbox, given that the input was not sanitized, \ are not properly handled and an attacker can build a path that is valid within the classpath.

Note: This vulnerability can only be exploited on Windows Operating Systems and Windows File Systems

Details

A Directory Traversal attack (also known as path traversal) aims to access files and directories that are stored outside the intended folder. By manipulating files with "dot-dot-slash (../)" sequences and its variations, or by using absolute file paths, it may be possible to access arbitrary files and directories stored on file system, including application source code, configuration, and other critical system files.

Directory Traversal vulnerabilities can be generally divided into two types:

  • Information Disclosure: Allows the attacker to gain information about the folder structure or read the contents of sensitive files on the system.

st is a module for serving static files on web pages, and contains a vulnerability of this type. In our example, we will serve files from the public route.

If an attacker requests the following URL from our server, it will in turn leak the sensitive private key of the root user.

curl http://localhost:8080/public/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/root/.ssh/id_rsa

Note %2e is the URL encoded version of . (dot).

  • Writing arbitrary files: Allows the attacker to create or replace existing files. This type of vulnerability is also known as Zip-Slip.

One way to achieve this is by using a malicious zip archive that holds path traversal filenames. When each filename in the zip archive gets concatenated to the target extraction folder, without validation, the final path ends up outside of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicious file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:

2018-04-15 22:04:29 .....           19           19  good.txt
2018-04-15 22:04:42 .....           20           20  ../../../../../../root/.ssh/authorized_keys

CVSS Scores

version 3.1
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Snyk

4.8 medium
  • Attack Vector (AV)
    Network
  • Attack Complexity (AC)
    High
  • Privileges Required (PR)
    None
  • User Interaction (UI)
    None
  • Scope (S)
    Unchanged
  • Confidentiality (C)
    Low
  • Integrity (I)
    Low
  • Availability (A)
    None
Expand this section

NVD

5.3 medium
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Red Hat

5.3 medium