What Are Server-Side Vulnerabilities?
The term “server-side vulnerabilities” describes weak points or defects in a computer system’s server-side components that can be used by attackers to obtain unauthorized access, interrupt services, or steal confidential information.
Web servers, application servers, database servers, and server-side scripting languages are just a few examples of the server infrastructure components that could have these vulnerabilities.
Code injection, poor input validation, unsafe file uploads, unsafe direct object references, and configuration errors are examples of common server-side vulnerabilities. Exploiting these flaws could have disastrous repercussions including compromised servers, data breaches, and unauthorized privilege escalation.
To ensure the security and integrity of their systems, it is essential for organizations to proactively discover and fix server-side vulnerabilities.
1. SQL Injection In Server-Side Vulnerabilities
When hostile actors use an online application’s inadequate input validation to inject and execute malicious SQL code within a database query, this situation is known as SQL injection, and it is a common and serious server-side vulnerability.
Attackers have the ability to alter the intended behavior of the application, get unauthorized access to sensitive data, edit or delete data, or even take over the entire database server by entering malicious SQL queries.
Attacks using SQL injection are especially risky since they can result in data breaches, data loss, and unauthorized system access. Implementing effective input validation and parameterized queries, conducting frequent security audits, and applying security patches and updates to stop potential exploitation are all crucial for mitigating SQL injection issues.
SQL Injection Labs We Have Covered:
- SQL injection vulnerability in WHERE clause allowing retrieval of hidden data
- SQL injection vulnerability allowing login bypass
- SQL injection UNION attack, determining the number of columns returned by the query
- SQL injection UNION attack, finding a column containing text
- SQL injection UNION attack, retrieving data from other tables
- SQL injection UNION attack, retrieving multiple values in a single column
- SQL injection attack, querying the database type and version on Oracle
- SQL injection attack, querying the database type and version on MySQL and Microsoft
- SQL injection attack, listing the database contents on non-Oracle databases
- SQL injection attack, listing the database contents on Oracle
- Blind SQL injection with time delays
- Blind SQL injection with out-of-band interaction
- Blind SQL injection with out-of-band data exfiltration
- SQL injection with filter bypass via XML encoding
2. Authentication vulnerabilities In Server-Side Vulnerabilities
Authentication vulnerabilities refer to weaknesses or flaws in the authentication mechanisms used to verify the identity of users and grant them access to systems, applications, or resources. These vulnerabilities can lead to unauthorized access, privilege escalation, and compromise of sensitive information.
Common authentication vulnerabilities include weak or easily guessable passwords, lack of multifactor authentication, improper session management, and insecure password storage practices. Attackers can exploit these vulnerabilities to impersonate legitimate users, bypass authentication controls, and gain unauthorized access to sensitive data or systems.
Organizations should implement strong authentication measures, such as enforcing complex passwords, implementing multifactor authentication, using secure protocols, and regularly auditing and updating authentication systems to address any potential vulnerabilities and protect against unauthorized access.
Authentication vulnerabilities Labs We Have Covered:
- Username enumeration via Different responses
- 2FA simple Bypass
- Password Reset Broken Logic
- Username Enumeration Via Subtly different Responses
- Username Enumeration via response timing
- Broken brute-force protection, IP block
- Username Enumeration via Account Lock
- 2FA Broken Logic
- Offline Password Cracking
- Password Reset Poisoning via Middleware
- Password Brute-force via Password Change
- Broken Brute-Force Protection, Multiple Credentials Per Request
- 2FA Bypass using a Brute-Force Attack
3. Directory Traversal In Server-Side Vulnerabilities
A server-side vulnerability called directory traversal, also referred to as path traversal or directory climbing, arises when an attacker is able to travel past the web application’s intended directory structure and access files or folders that are outside the permitted scope.
Typically, this vulnerability is taken advantage of by changing input parameters that include file paths or directory names. Attackers can climb the directory tree and access private files or run arbitrary commands on the server by using “../” or other specially designed sequences.
Attacks that include directory traversal may lead to unauthorized access to important files, the disclosure of private data, and even the execution of remote code. Input validation and appropriate sanitization of user-supplied input should be implemented to ensure that file paths are valid to prevent directory traversal issues.
Directory Traversal Labs We Have Covered:
- File path traversal, simple case
- File path traversal, traversal sequences blocked with absolute path bypass
- File path traversal, traversal sequences stripped non-recursively
- File path traversal, traversal sequences stripped with superfluous URL-decode
- File path traversal, validation of start of path
- File path traversal, validation of file extension with null byte bypass
4. Command Injection In Server-Side Vulnerabilities
Insufficient input validation or incorrect handling of user-supplied input in a web application or command-line interface can allow an attacker to execute arbitrary commands on a target system, which is known as command injection.
By taking advantage of flaws such a lack of input sanitization, inappropriate use of system calls, or unsecure usage of user input during command execution, attackers can insert malicious commands. When exploited effectively, command injection can result in unauthorized command execution, system compromise, data leaks, or even total control over the intended system.
It is essential to implement correct input validation, clean user input, use parameterized queries or prepared statements, and make sure that user-supplied input is not simply concatenated into command strings in order to avoid command injection issues.
Command Injection Labs We Have Covered:
- OS Command Injection, Simple Case
- Blind OS Command Injection With Time Delays
- Blind OS Command Injection With Output Redirection
- Blind OS Command Injection With Out-Of-Band Interaction
- Blind OS Command Injection With Out-Of-Band Data Exfiltration
5. Information Disclosure In Server-Side Vulnerabilities
The term “information disclosure” describes the unintentional exposure or leakage of confidential information. It is a server-side vulnerability that happens when programs, websites, or other software unintentionally leak private information to third parties.
This vulnerability may show up in a variety of ways, including error messages that reveal sensitive information or system information, directory listings that show file names and directory structures, configuration files with sensitive information, or data that has been sent or stored insecurely.
The release of personally identifiable information, trade secrets, or proprietary data, which can result in identity theft, fraud, or reputational harm, can have serious repercussions.
Information Disclosure Labs We Have Covered:
- Information Disclosure In Error Messages
- Information Disclosure On Debug Page
- Source Code Disclosure Via Backup Files
- Authentication Bypass Via Information Disclosure
- Information Disclosure In Version Control History
- Automate Information Disclosure Vulnerabilities
Access Control In Server-Side Vulnerabilities
The techniques and guidelines put in place to govern and manage user access to resources or functions within a system or application are referred to as access control.
Users are provided the proper permissions depending on their jobs and responsibilities when access control is done properly. When there are errors in the conception or application of access control measures, it might result in unauthorized access or privilege escalation.
To reduce access control vulnerabilities and uphold the security and integrity of systems and data, it is essential to implement strict access controls, such as authentication, authorization, and the least privilege principle.
Access Control Labs We Have Covered:
- Unprotected admin functionality
- Unprotected admin functionality with unpredictable URL
- User role controlled by request parameter
- User role can be modified in user profile
- User ID controlled by request parameter with password disclosure
- User ID controlled by request parameter, with unpredictable user IDs
- User ID controlled by request parameter with data leakage in redirect
- User ID controlled by request parameter with password disclosure
- Insecure direct object references
- URL-based access control can be circumvented
- Method-based access control can be circumvented
- Multi-step process with no access control on one step
- Referer-based access control
XXE Injection In Server-Side Vulnerabilities
A server-side vulnerability known as XXE injection occurs when an attacker uses unsafe XML parsing to incorporate foreign entities or files. An attacker can read private files, start denial-of-service attacks, or carry out SSRF (Server-Side Request Forgery) by inserting specially prepared XML input.
Implementing appropriate input validation, blocking or limiting external entity resolution, and utilizing secure parsing libraries that guard against entity expansion attacks are all necessary to mitigate XXE injection issues.
XXE Injection Labs We Have Covered:
- Exploiting XXE using external entities to retrieve files
- Exploiting XXE to perform SSRF attacks
- Blind XXE with out-of-band interaction
- Blind XXE with out-of-band interaction via XML parameter entities
- Exploiting blind XXE to exfiltrate data using a malicious external DTD
- Exploiting blind XXE to retrieve data via error messages
- Exploiting XInclude to retrieve files
- Exploiting XXE via image file upload
- Exploiting XXE to retrieve data by repurposing a local DTD
File Upload Vulnerabilities In Server-Side Vulnerabilities
When an application fails to properly validate or sanitize user-uploaded files, file upload vulnerabilities appear, enabling attackers to upload malicious files and run arbitrary server code.
Such flaws may allow remote code execution, server compromises, or unauthorized access. It is crucial to enforce file size restrictions, use secure file storage sites, validate file types, and put security measures like virus scanning into place in order to prevent file upload risks.
File Upload Vulnerabilities Labs We Have Covered:
- Remote code execution via web shell upload
- Web shell upload via Content-Type restriction bypass
- Web shell upload via path traversal
- Web shell upload via extension blacklist bypass
- Web shell upload via obfuscated file extension
Business Logic Vulnerabilities In Server-Side Vulnerabilities
When certain business rules and logic are implemented incorrectly by the application, business logic vulnerabilities result. Attackers may use these flaws to circumvent intended functionality, alter data, or obtain unauthorized access.
Each application has its own set of business logic vulnerabilities that must be thoroughly examined and tested in order to be found and efficiently fixed. Business logic vulnerabilities can be reduced with the aid of routine security testing, code reviews, and the implementation of appropriate input validation.
Business Logic Vulnerabilities Labs We Have Covered:
- Excessive trust in client-side controls
- High-level logic vulnerability
- Inconsistent security controls
- Flawed enforcement of business rules
- Low-level logic flaw
- Inconsistent handling of exceptional input
- Weak isolation on dual-use endpoint
- Insufficient workflow validation
- Authentication bypass via flawed state machine
- Infinite money logic flaw
- Authentication bypass via encryption Oracle
Server-Side Request Forgery (SSRF) In Server-Side Vulnerabilities
A server-side vulnerability known as Server-Side Request Forgery SSRF allows an attacker to trick a server into sending unauthorized queries to internal or external resources. Attackers are able to get around access constraints, access internal resources, and launch assaults against other systems by taking use of SSRF.
Validating and sanitizing user-supplied input, imposing stringent access controls, and establishing whitelisting or firewall rules to limit outbound requests to trustworthy resources are all necessary for the prevention of SSRF vulnerabilities.
Server-Side Request Forgery (SSRF) Labs We Have Covered:
- Basic SSRF against the local server
- Basic SSRF against another back-end system
- SSRF with blacklist-based input filter
- SSRF with filter bypass via open redirection vulnerability
- Blind SSRF with out-of-band detection
- SSRF with whitelist-based input filter
- Blind SSRF with Shellshock Exploitation
A thorough review of the many vulnerabilities that might jeopardize the security of server infrastructure, applications, and databases is provided by the Complete Road Map to Server-Side Vulnerabilities 2023. Organizations can proactively strengthen their systems and defend against malicious assaults by being aware of these vulnerabilities and their possible effects.
Additionally, this road map offers workable remedies through a number of completed laboratories in addition to highlighting the weaknesses. These laboratories are useful tools for learning by doing and comprehending how attackers operate. Organizations and individuals can improve their knowledge and talents in locating, minimizing, and securing server-side vulnerabilities by participating in these laboratories.
To maintain a strong security posture, it’s essential to keep up with the most recent security techniques, patch and upgrade systems often, and perform regular security assessments.
Organizations and individuals can now navigate the complicated world of server-side vulnerabilities, secure their systems, and shield sensitive data from hackers thanks to the Complete Road Map to Server-Side Vulnerabilities 2023 and the solved labs that go along with it. We can all work together to increase the resilience of our server infrastructure and provide a safer digital environment by putting the best practices recommended in this road map into practice and developing a proactive security mentality.