A07:2025 – Identification and Authentication Failures
Overview
Identification and Authentication Failures cover weaknesses that allow attackers to impersonate users, bypass authentication controls, or take over accounts. In the OWASP Top 10:2025, this category remains critical because authentication is still the primary gatekeeper for most applications — and when it fails, everything behind it becomes exposed.
Unlike injection or misconfiguration, authentication failures directly undermine identity. If an application cannot reliably determine who a user is, every authorization decision built on top of that identity becomes meaningless.
From an attacker’s perspective, authentication failures are high-value because:
they often allow access without exploiting complex bugs
they can be automated at scale
they blend into normal login behavior
successful exploitation provides legitimate sessions
Identification vs Authentication
A key concept in A07 is the distinction between identification and authentication.
Identification answers: Who are you claiming to be? (e.g., username, email, account ID)
Authentication answers: Can you prove it? (e.g., password, token, biometric, MFA)
Failures can occur in either stage, or in how they are combined.
An application may correctly identify a user but authenticate them weakly, or authenticate successfully while trusting an incorrect identity context.
Authentication Is a System, Not a Feature
Authentication failures rarely exist in isolation. They usually involve a combination of:
credential handling
session management
token generation
password policies
multi-factor logic
error handling
rate limiting
recovery mechanisms
An application may implement authentication “correctly” in one place and fail in another. Attackers look for these inconsistencies.
Why Authentication Still Fails in Modern Applications
Despite mature frameworks and widespread awareness, authentication failures persist because:
legacy mechanisms coexist with modern ones
usability is prioritized over security
developers trust default configurations
recovery flows receive less scrutiny
APIs and mobile clients introduce new paths
assumptions are made about user behavior
Authentication is often implemented incrementally, not holistically.
Authentication Failures Often Enable Everything Else
Once authentication is compromised, attackers can:
bypass access control entirely
exploit business logic flaws
access sensitive data
perform actions as legitimate users
evade detection
In many real-world incidents, authentication failure is the first successful step, not the final exploit.
Common Impact of A07 Failures
Authentication failures can lead to:
account takeover
credential stuffing success
session hijacking
unauthorized access to APIs
privilege escalation
data exposure
Because the attacker operates as a valid user, exploitation often leaves minimal forensic traces.
Authentication in Modern Architectures
In modern applications, authentication failures frequently appear in:
APIs using token-based auth
mobile backends
single sign-on (SSO) integrations
OAuth and federated identity flows
microservices trusting upstream identity
custom authentication logic
Each added integration increases complexity and expands the attack surface.
Attacker Perspective
From an offensive mindset, authentication testing revolves around one question:
“How can I become someone else — or avoid proving who I am?”
Attackers test:
credential handling
session behavior
token integrity
recovery mechanisms
rate limits
edge cases
They assume that at least one path will be weaker than the rest.
What Are Identification and Authentication Failures?
Identification and Authentication Failures occur when an application cannot reliably verify the identity of a user, or when the mechanisms used to prove that identity can be bypassed, abused, or weakened.
In these scenarios, the application either:
allows attackers to assume another user’s identity, or
grants access without sufficient proof of identity
From an attacker’s perspective, authentication failures are ideal because they provide legitimate access. The attacker is not breaking into the system — they are logging in, reusing sessions, or abusing flows that the application explicitly provides.
Authentication Is More Than Login
A common mistake is treating authentication as a single event: the login form.
In reality, authentication includes:
how users are identified
how credentials are validated
how sessions are created and maintained
how tokens are issued and verified
how authentication state is enforced
how identity is propagated across services
A failure in any of these areas can undermine the entire authentication system.
Identification Failures
Identification failures occur when the application incorrectly determines who the user is.
Examples include:
user identifiers that can be guessed or enumerated
ambiguous or non-unique usernames
case-insensitive comparisons causing collisions
trusting client-provided identity fields
mixing multiple identity sources inconsistently
If identification is flawed, authentication may succeed — for the wrong user.
Authentication Failures
Authentication failures occur when the application does not adequately verify proof of identity.
Common causes include:
weak password policies
missing or optional multi-factor authentication
brute-forceable login endpoints
predictable or reusable tokens
flawed credential validation logic
From an attacker’s perspective, authentication fails whenever the cost of impersonation is low.
Authentication State and Session Failures
Authentication does not end after login.
Failures also occur when:
sessions are not invalidated properly
tokens remain valid longer than intended
authentication state can be reused across contexts
logout does not terminate access
session fixation is possible
These issues allow attackers to retain access even after credentials change.
Authentication Recovery Is Often the Weakest Link
Password reset and account recovery mechanisms are frequent sources of authentication failures.
These flows often:
lack rate limiting
rely on guessable tokens
expose account existence
trust user-controlled inputs
bypass multi-factor checks
Attackers target recovery flows because they are:
less tested
designed for convenience
rarely monitored closely
APIs and Authentication Failures
APIs frequently introduce authentication failures because:
they assume trusted clients
they reuse tokens across services
they lack user interaction constraints
they expose direct authentication endpoints
An authentication system that works for a web UI may fail when exposed via APIs.
Authentication vs Authorization Confusion
A recurring failure pattern is treating authentication as authorization.
Examples include:
assuming “logged in” means “allowed”
trusting role claims without validation
skipping authorization checks after authentication
Authentication answers who you are. Authorization answers what you can do.
Confusing the two leads directly to privilege escalation.
Why These Failures Persist
Identification and authentication failures persist because:
they span multiple components
they evolve over time
they are impacted by usability trade-offs
they rely on correct configuration everywhere
they are difficult to test exhaustively
Attackers rely on inconsistency.
Attacker Perspective
From an offensive point of view, authentication failures mean:
“The system believes I am someone I am not.”
Once that belief is established, the attacker does not need further exploitation.
Common Identification and Authentication Failure Scenarios
Identification and authentication failures tend to appear in recurring patterns. These are not exotic attacks, but predictable weaknesses that emerge when identity, credentials, and session state are not treated as a cohesive system.
Below are the most common authentication failure scenarios observed during real-world offensive testing.
Weak Password Policies
Weak password policies significantly reduce the cost of impersonation.
This includes:
short minimum length
lack of complexity requirements
no protection against common or breached passwords
password reuse across accounts
no enforcement of rotation after compromise
From an attacker’s perspective, weak password policies enable:
brute-force attacks
credential stuffing
account takeover at scale
Strong cryptography does not help if the password itself is weak.
Brute-Force and Credential Stuffing
Authentication endpoints that lack proper protections are prime targets.
Common design and implementation failures include:
missing rate limiting
unlimited login attempts
lack of IP or account throttling
no detection of abnormal login behavior
Attackers automate login attempts using:
leaked credential databases
username enumeration
password spraying techniques
If the system allows unlimited attempts, it will be abused.
Account Enumeration via Authentication Responses
Authentication flows often leak information about account existence.
Examples include:
different error messages for “user not found” vs “wrong password”
different response times
different HTTP status codes
password reset flows that confirm account existence
These leaks allow attackers to:
enumerate valid users
target specific accounts
optimize brute-force and phishing attacks
From an offensive perspective, enumeration is the first step toward compromise.
Insecure Password Recovery and Reset
Password recovery flows are one of the most common sources of authentication failures.
Typical issues include:
predictable or reusable reset tokens
tokens without expiration
lack of binding to user or session
no rate limiting
bypass of MFA during reset
Attackers focus on recovery mechanisms because they are often less protected than login flows.
Missing or Weak Multi-Factor Authentication (MFA)
MFA is often:
optional
inconsistently enforced
bypassable under certain conditions
Common failure patterns include:
MFA enforced only on login, not on sensitive actions
MFA skipped for “trusted” devices
MFA disabled during recovery flows
weak second factors (SMS-only, predictable OTPs)
From an attacker’s view, partial MFA is almost as good as no MFA.
Session Fixation and Session Reuse
Authentication failures frequently involve session handling.
Common issues include:
session identifiers not rotated after login
reuse of pre-authentication sessions
predictable or long-lived session IDs
tokens reused across contexts
These flaws allow attackers to:
hijack authenticated sessions
persist access after credential changes
impersonate users without knowing passwords
Token-Based Authentication Failures
Modern applications rely heavily on tokens (JWT, API tokens, OAuth tokens).
Failures include:
weak signing algorithms
accepting unsigned tokens
trusting token claims blindly
missing validation of audience or issuer
excessive token lifetimes
Attackers manipulate tokens to:
escalate privileges
impersonate users
bypass authentication entirely
Authentication Bypass via Alternate Paths
Authentication may be enforced in one path but missing in another.
Common examples:
APIs less protected than UI
legacy endpoints
mobile backends
debug or internal routes
misconfigured SSO callbacks
Attackers avoid the main door and look for side entrances.
Logout and Session Termination Failures
Logout is often treated as a UI feature, not a security control.
Failures include:
logout not invalidating sessions
tokens remaining valid after logout
sessions persisting across password changes
shared sessions across devices
From an attacker’s perspective: If logout does not revoke access, it does not exist.
Why These Scenarios Matter
These scenarios show that authentication failures are rarely about one broken control. They are about incomplete identity lifecycle management.
Attackers do not need to defeat authentication entirely — they only need to find one weak point.
Testing Perspective (Offensive Mindset)
Testing authentication is not about checking whether a login form exists. From an offensive perspective, it is about breaking the assumptions the application makes about identity, trust, and session state.
Attackers do not ask:
“Does authentication work?”
They ask:
“Where does authentication stop working consistently?”
Treat Authentication as an Attack Surface, Not a Feature
Authentication spans multiple components and moments in time:
login
session creation
token issuance
token validation
session reuse
logout
recovery flows
Attackers test authentication as a system, not as a single endpoint.
A failure anywhere in that system can invalidate the entire identity model.
Start With Enumeration and Signal Gathering
Before attempting bypasses, attackers look for signals.
They observe:
error messages
response codes
response timing
differences between valid and invalid users
behavior changes after multiple attempts
Even subtle differences can confirm:
account existence
credential validity
backend logic paths
Enumeration is often silent and low risk.
Assume Brute Force Is Possible Until Proven Otherwise
From an offensive standpoint, brute force is always tested.
Attackers verify:
rate limiting on login endpoints
rate limiting per account vs per IP
throttling behavior
lockout thresholds
detection of automation
If no clear resistance exists, automation follows.
Test Authentication in Context
Authentication behavior often changes based on:
user role
authentication method
device or client
API vs UI
time or location
Attackers test:
low-privileged users
newly created accounts
accounts with partial setup
edge-case roles
service or system accounts
Inconsistent enforcement is a strong indicator of failure.
Focus on Token and Session Behavior
Modern authentication relies heavily on tokens and sessions.
Attackers analyze:
token structure and claims
signing and validation logic
token lifetime and reuse
context binding
revocation behavior
They test whether:
tokens can be replayed
tokens work across users or roles
claims can be manipulated
expired tokens are rejected
If tokens outlive trust, authentication is broken.
Abuse Recovery and Secondary Flows
Recovery flows are often less protected.
Attackers target:
password reset
email verification
MFA reset
account unlock
“remember me” functionality
They test whether recovery:
bypasses MFA
leaks account existence
allows token reuse
lacks expiration
can be abused at scale
Many real-world compromises start here.
Test Logout and Session Termination
Attackers assume logout is cosmetic until proven otherwise.
They verify:
whether sessions are invalidated
whether tokens are revoked
whether sessions persist across devices
whether password changes kill active sessions
Persistent sessions equal persistent access.
Test Alternate Authentication Paths
Authentication is often enforced differently across:
APIs
mobile backends
legacy endpoints
internal services
SSO callbacks
Attackers look for the weakest path, not the most obvious one.
Authentication Failures Are Often Silent
Many authentication attacks:
do not trigger errors
resemble normal login behavior
generate valid sessions
avoid detection
This makes them ideal for long-term exploitation.
Final Offensive Principle
Authentication testing is about answering one question:
“What does the application trust about identity that I can manipulate?”
If identity can be influenced, reused, or bypassed, authentication has failed.
Hands-on Testing Checklist – Identification and Authentication Failures (A07:2025)
This checklist is designed for active offensive testing of identification and authentication mechanisms. It focuses on how identity is established, proven, maintained, and terminated, not just on login functionality.
The guiding principle is:
If identity can be influenced, reused, or bypassed, authentication has failed.
Final Attacker Mindset
Authentication testing is about becoming someone else without resistance.
If the application assumes:
“users won’t try this”
“this flow is rarely used”
“this client is trusted”
“this token is safe”
That assumption is the vulnerability.
Last updated