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Authentication and access controls play a crucial role in web application and system security. If these controls are weak or inconsistent, it can create a vulnerability threat actors can easily exploit via an authentication bypass.
Summary: Authentication bypass vulnerabilities allow attackers to gain unauthorized access without valid credentials by exploiting weaknesses in authentication mechanisms. These vulnerabilities can lead to data theft, system compromise, and privilege escalation. Organizations can prevent authentication bypass through regular patching, multi-factor authentication, encryption, and strong password policies.
What is authentication bypass?
An authentication bypass vulnerability occurs when an attacker bypasses the authentication mechanisms of a device to gain unauthorized access. It can happen when an application fails to verify the identity of a user before granting access. This type of flaw is closely related to security bypass vulnerabilities, which allow attackers to circumvent security controls entirely.
According to the Common Attack Pattern Enumeration and Classification (CAPEC), an attacker gains access, similar to an authenticated user, without going through the authentication process. They further state that "this is usually the result of the attacker using an unexpected access procedure that does not go through the proper checkpoints where authentication should occur."
How does authentication bypass work?
For many users, a simple example of an authentication bypass is when a bad actor accesses an application with another user's credentials, such as their email address and password. If multi-factor authentication is not installed, anyone can access that application with just those credentials. Attackers have gotten savvy in exploiting applications with even more security authentication controls in place.
The vulnerability exploited is technically a weakness in the design of an application that allows an attacker to authenticate and escalate privileges without proper credentials.
In some cases, these vulnerabilities are used by attackers to gain unauthorized access to systems or data. For example, suppose someone attempts to log into a server but does not have permission granted by an administrator. In that case, they could use an authentication bypass vulnerability on that server's login page to obtain unauthorized access.
Attackers can also use this exploit by bypassing the authentication process to steal user session cookies or valid session IDs. For example, the attacker can create a legitimate admin session with the 'username=admin' cookie in the HTTP request code. Once accessed, they can download harmful firmware and modify the system settings.
What are recent examples of authentication bypass vulnerabilities?
Each of these vulnerabilities has a CVE identifier, which provides standardized tracking and scoring for security flaws.
| CVE | Product | Year | Description |
|---|---|---|---|
| CVE-2024-21762 | Fortinet FortiOS | 2024 | Out-of-bounds write allowing remote code execution without authentication |
| CVE-2024-3400 | Palo Alto PAN-OS | 2024 | Command injection in GlobalProtect enabling unauthenticated access |
| CVE-2024-27198 | JetBrains TeamCity | 2024 | Authentication bypass allowing admin account creation |
| CVE-2025-0282 | Ivanti Connect Secure | 2025 | Stack-based buffer overflow enabling pre-authentication remote code execution |
| CVE-2024-55591 | Fortinet FortiOS | 2025 | Authentication bypass via crafted requests to Node.js websocket module |
What is the impact of authentication bypass?
Authentication bypass is one of the most common security threats that can compromise data integrity. There can be several damaging effects that might occur with an authentication bypass vulnerability.
Here are the most common types of impact when attackers use authentication bypass to compromise user access control and steal data:
Data theft from unauthorized parties - Attackers access sensitive information without proper credentials
Risk of data loss - Attackers steal or destroy information stored on a device or server
Data corruption - Unauthorized users change information stored in the system
Data manipulation - Malicious actors infiltrate a system and alter input information before storage
How can you mitigate authentication bypass vulnerabilities?
Authentication bypass vulnerabilities are primarily a result of weak authentication mechanisms. Automox recommends the following efforts and tasks for the fastest path to addressing these vulnerabilities in your organization:
1. Patch frequently and often
Keep your apps and servers up to date with the latest updates to block attackers, stopping them in their tracks. Research shows that nearly 60% of data breaches trace back to unpatched vulnerabilities, making timely patching critical for authentication security.
2. Enforce strong security controls
Setting stringent access policies and authentication enforcements such as multi-factor authentication (MFA) can immediately block bad actors' access. Follow endpoint security best practices to ensure your systems are protected at every entry point.
3. Encrypt where and when you can
From user session IDs to cookies, enabling encryption can ruin an attacker's day. Encryption makes stolen session data useless without the corresponding decryption keys.
4. Secure your data files and folders
As many apps and servers default to unsecured states, ensure you update and secure them promptly with strong passwords.
Authentication bypass prevention comparison
| Prevention Method | Effectiveness | Implementation Difficulty | Implementation Cost |
|---|---|---|---|
| Multi-factor authentication (MFA) | High | Low | Low to Medium |
| Regular patching | High | Medium | Low |
| Session encryption | Medium to High | Medium | Low |
| Strong password policies | Medium | Low | Low |
| Access control audits | High | High | Medium |
| Web application firewall | Medium to High | Medium | Medium to High |
Fight the good fight against malicious actors
When dealing with bad actors, organizations must stay vigilant. Criminals do not take breaks. They use every opportunity to exploit vulnerabilities.
Similarly, security teams cannot let their guard down. Triple-check that your access controls are stringent and continually up-to-date.
Frequently Asked Questions
Authentication bypass occurs when attackers skip the process of proving their identity entirely. Authorization bypass happens after authentication, when an authenticated user accesses resources beyond their permitted scope. Both vulnerabilities can lead to unauthorized access, but they target different stages of the access control process.
Multi-factor authentication significantly reduces the risk of authentication bypass but cannot prevent all attacks. Attackers may still exploit vulnerabilities in the MFA implementation itself, use session hijacking after successful authentication, or target applications that do not properly enforce MFA across all entry points.
Organizations should patch critical authentication bypass vulnerabilities within 24 to 48 hours of patch availability, especially for internet-facing systems. The 2025 Ivanti and Fortinet vulnerabilities demonstrated that attackers actively exploit these flaws within days of public disclosure. Automated patching solutions help organizations meet these timelines consistently.
Security teams can use dynamic application security testing (DAST) tools, penetration testing frameworks, and vulnerability scanners to identify authentication bypass flaws. Regular security audits, code reviews, and bug bounty programs also help uncover these vulnerabilities before attackers exploit them.
Cloud applications face unique authentication bypass risks due to misconfigured identity providers, weak API authentication, and complex multi-tenant environments. The distributed nature of cloud infrastructure can create additional entry points that attackers may exploit. Proper configuration management and regular security assessments help mitigate these risks.
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