Diving into Authentication Vulnerabilities

Authentication, you may or may not have heard this word in your day to day life. But do you know what it means in cybersecurity context? If yes, that great and if partially yes, even better as you can refresh your understanding about this concept.

So what exactly is Authentication? In technical terms it is, "Authentication is the process of verifying the identity of a user, system, or entity to ensure they are who they claim to be before granting access to resources." What it basically means is that, Checking you are who you claim to be!

Authentication is a crucial security measure, helping to protect systems, data, networks, and applications from unauthorized access and potential attacks. In a way its like the first line of defense against attackers who might be out there for you and your precious data.

So as with any other concept, Authentication involves the following:

Something the user knows: Passwords or PINs.
Something the user has: OTPs, tokens, or devices.
Something the user is: Biometrics like fingerprints or facial recognition.

The types of Authentication consists of the above mentioned factors but for the sake of classification, it is classified something like:

1. Password based Authentication : Simple & most commonly used, where you enter password along with the username / email at the login page. 2. Certificate based Authentication: If remembering password sounds like a drag, this method uses a trusted digital certificate issued by a Certificate Authority (CA) to verify you or your device. 3. E-Token based Authentication: Or if you want to carry some hardware with you like movies, you carry a secure hardware token that authenticates you via stored cryptographic credentials or by generating One Time Passwords (OTPs). 4. Biometric based Authentication: And in case you dont wanna carry anything or remember your password, this method is the most suitable for you as it consists of you just being you and using your biometrics such as fingerprint, iris scan or facial recognition to authenticate you. 5. Application based Authentication: Lastly a type where you simply tap or enter the OTP generated by the authenticator apps to give you access to whatever you are trying to log into

Each & every method has its own pros and cons, so instead of using them one at a time try to utising two or more of them at a same time to decrease the chances of it being bypassed! Thats where Multi Factor Authentication (MFA) comes into play.The most common example being password based authentication followed by Application based authentication or some other form of OTP to gain access.

And for the beginners that mostly confuse Authentication with Authorisation, Just remember one thing. Authentication will always take place before authorisation. Authentication confirms your identity whereas Authorisation controls your access. Imagine you're entering an airport lounge. At the entrance, the staff checks your ID and boarding pass to confirm that you are really the person you claim to be. This is Authentication. Once they verify your identity, they then check what kind of ticket or membership you have. A regular economy ticket may only allow you into the main waiting area, while a business-class gives you access to premium lounges. This is Authorization determining what you are allowed to access after your identity has been confirmed.

How Authentication Breaks? Authentication rarely fails because of a single major flaw, it breaks due to small gaps in logic and implementation. Weak input handling, like predictable passwords or reusable OTPs, makes it easier for attackers to guess or reuse credentials without much effort. Authentication flows themselves are often flawed. If multi-step logins or 2FA checks are not properly enforced at every stage, attackers can skip steps or manipulate requests, especially when the system relies on client-side validation.Session management, missing or inconsistent authentication checks, or of abuse controls such as CAPTCHA and rate limiting also contribute to this.

And of course Authentication vulnerabilities can lead to severe consequences, including unauthorized access to sensitive data,financial losses, and damage to organizational reputation. There are several ways through which authentication vulnerabilities can arise. But following are the most common ones:

Flawed Brute-Force Protection
Weak Login Credentials
Username Enumeration
Poor Session Management
Insecure Password Change and Recovery
Flawed Two-Factor Authentication
Vulnerable Authentication Logic

And by solving Portswigger labs related to the above mentioned vulnerabilities related to Authentication, you can get a better understanding of each of these cases in detail.

The mitigations for Authentication vulnerabilities is as follows: -Implement proper Multi-Factor Authentication (MFA). -Enforce Strong Password Policies. -Implement Rate limiting, Account Lock out and bot detection mechanisms. -Secure Session Management. -Validate security checks at multiple points to avoid gaps in the flow. -Implement security controls to secondary or supporting features. -Prevent username enumeration.

Some real life scenarios where the Authentication related vulnerabilities wreaked havoc are as follows along with the references:

-A critical authentication bypass vulnerability in the Spirit Framework WordPress plugin , that affected all versions ≤ 1.2.14 (ref). -OneLogin authentication bypass on WordPress sites (ref). -Account Takeover via Auth Bypass in TikTok Account Recovery (ref). -Improper Authentication -2FA OTP Reusable (ref). -Authentication & Registration Bypass in Newspack Extended Access(ref)

P.S. All images are generated by AI and for better understanding of concepts after going through the theory.

References: https://portswigger.net/web-security/authentication https://owasp.org/Top10/2025/A07_2025-Authentication_Failures/ https://www.strongdm.com/blog/authentication-vulnerabilities https://github.com/nikhilkumar0102/Cyber-Lab-Writeups/blob/main/OWASP-Top10%20Broken%20Authentication.pdf