Authentication is supposed to answer one simple question: Who are you?
When that answer can be forged, guessed, reused, or automated, attackers do not need sophisticated exploits. They just sign in.
OWASP A07:2025 – Authentication Failures focuses on security weaknesses that allow attackers to compromise accounts, steal identities, and impersonate users across applications and APIs. Despite years of awareness, authentication failures remain one of the most exploited risks because they target the very foundation of trust in modern digital systems.
What Is OWASP A07:2025 Authentication Failures?
OWASP A07:2025 – Authentication Failures refers to weaknesses in how applications and APIs verify user identities and manage authentication workflows. These failures occur when authentication mechanisms are poorly designed, inconsistently enforced, or unable to withstand automated abuse.
Authentication failures often emerge when applications rely on weak password policies, fail to protect login endpoints from , mishandle session tokens, or assume that identity providers and frameworks automatically solve authentication security. In many cases, authentication works “well enough” for normal users but collapses under automated attack.
Authentication failures frequently impact entire user populations. Once an attacker gains valid credentials or tokens, they are logging in exactly as designed but with malicious intent.
The OWASP Top 10 2025 highlights authentication failures as a persistent risk because modern applications increasingly depend on APIs, distributed identity systems, and automated access, dramatically expanding the authentication attack surface.
Why Authentication Failures Are a Top Risk in OWASP Top 10 2025
Authentication failures persist because identity systems have become more complex while enforcement remains inconsistent.
Automation has changed the threat model
Credential stuffing and password spraying use billions of leaked credentials and operate at machine speed. A login form that feels secure to a human user can be trivial for a botnet to abuse.
Imagine a SaaS login page that allows five failed attempts before locking an account. To a developer, that sounds reasonable. To an attacker controlling thousands of IP addresses, it means five guesses per IP, multiplied endlessly. The lockout exists, but the design never accounted for distributed automation.
APIs silently expand authentication exposure
APIs frequently handle authentication tokens, session identifiers, and API keys. These endpoints are often less protected than user-facing login pages.
For example, a mobile app may authenticate users through an API endpoint that validates tokens but lacks rate limiting or behavioral checks. An attacker does not need to attack the UI at all. They can go straight to the API and replay tokens or test credentials at scale, bypassing protections that only exist at the frontend.
Overreliance on identity providers
Single sign-on, OAuth, and external identity providers are widely used and often trusted implicitly. While these systems handle identity verification, they do not protect applications from abuse.
If an application does not enforce rate limits, session validation, or anomaly detection at its own layer, attackers can still abuse valid credentials obtained elsewhere. Inconsistent controls across channels
Authentication may be tightly protected on the web application but weak on mobile apps, APIs, legacy endpoints, or partner integrations. Attackers naturally gravitate to the weakest path.
Common Authentication Failures in Production Applications
Authentication failures appear repeatedly across real-world environments in the below forms.
Weak or reused credentials
Applications that allow simple passwords or fail to protect against reused credentials make attackers’ jobs easy. Leaked credentials from previous breaches are constantly tested against new targets.
Missing protection against credential stuffing
Many login endpoints lack effective rate limiting, bot detection, or behavioral analysis. Attackers can test millions of credentials while appearing as normal traffic.
Insecure session and token handling
Authentication tokens that are long-lived, predictable, or reused across services allow attackers to replay sessions even after the initial compromise.
Consider a token that never expires and is accepted by multiple APIs. Once stolen, it becomes a permanent master key.
Incomplete or bypassable MFA
Multi-factor authentication may exist but only for certain users or workflows. Attackers routinely look for alternate login paths that bypass MFA entirely, such as legacy endpoints or API-based authentication flows.
API authentication gaps
APIs sometimes trust that a request is “internal” or “already authenticated” without re-validating tokens properly. These assumptions collapse immediately when APIs are exposed externally.
Authentication Failures vs. Authorization Failures
Authentication and authorization are often confused, but they answer different questions.
| Aspect | Authentication Failures | Authorization Failures |
|---|---|---|
| Core question | Who are you? | What are you allowed to do? |
| Root issue | Identity verification | Permission enforcement |
| Typical impact | Account takeover | Data or privilege abuse |
| Example | Stolen credentials | Accessing another user’s data |
Authentication failures allow attackers to become someone else. Everything that follows becomes easier.
Business Impact of Authentication Failures
Authentication failures hit the business fast. Once an attacker gets in with real credentials or a valid session, they can commit fraud, pull sensitive data while “looking normal,” and move across connected apps and APIs. The visible costs stack up: customer churn, slowed new sales, forced resets, support spikes, forensics, and audits. In regulated industries, the legal and disclosure burden can outlast the incident.
Real incidents show how quickly this turns into dollars and brand damage. MGM told investors its 2023 cyber incident drove about a $100 million hit to adjusted property EBITDAR (Las Vegas Strip + regional ops) and added under $10 million in one-time expenses, alongside exposure of customer personal data. 23andMe said attackers used credential stuffing to access roughly 14,000 accounts and then reach data in millions of connected profiles, after which the company forced password resets and required two-step verification for all users.
How Attackers Exploit Authentication Failures
Attackers rarely target authentication through simple guessing. Modern exploitation relies on automation, leaked data ecosystems, API abuse, and logic weaknesses that allow attacks to scale quietly across thousands of accounts.
Credential stuffing at massive scale
Attackers aggregate billions of leaked credentials from previous breaches, dark web markets, malware logs, and phishing kits. These credentials are automatically tested across web apps, mobile apps, and API login endpoints. Even a 0.5–1% success rate can compromise thousands of accounts in minutes. Poor bot detection, weak rate limiting, and inconsistent API protections make these attacks extremely effective.
Password spraying to bypass lockout controls
Instead of hammering a single account, attackers try common passwords (like seasonal patterns or company-related terms) across large user populations. This avoids triggering brute-force alerts while still generating high takeover success. Organizations with weak monitoring often miss these slow-burn attacks for weeks.
Session hijacking and token replay
Stolen cookies, OAuth tokens, JWTs, and API keys obtained via malware, browser injections, phishing pages, or insecure storage are reused to bypass authentication entirely. Many applications fail to bind sessions to devices, IP reputation, or behavior patterns, allowing attackers to operate indefinitely as legitimate users.
Multi-factor authentication bypass techniques
Attackers increasingly target MFA logic rather than passwords themselves — using push fatigue attacks, real-time phishing proxies that capture one-time codes, SIM swapping, or exploiting poorly implemented fallback flows such as SMS resets or backup codes.
Authentication workflow logic flaws
Weak password reset mechanisms, predictable token generation, insecure email verification links, improper account lock handling, and broken “remember me” implementations allow attackers to gain access without valid credentials. These are often overlooked because they are business logic issues, not classic vulnerabilities.
API-driven authentication abuse
APIs frequently expose raw authentication endpoints with fewer protections than web login pages. Attackers directly brute-force credentials, replay tokens, enumerate users, and bypass CAPTCHA or behavioral defenses by targeting backend services used by mobile apps and integrations.
Account enumeration and reconnaissance
Subtle response differences during login, reset requests, or signup flows allow attackers to identify valid usernames and emails at scale. These confirmed accounts are then fed into credential stuffing and phishing campaigns for higher success rates.
Phishing combined with real-time automation
Modern phishing kits act as live proxies; victims enter credentials and MFA codes which are immediately relayed to attackers who log in before the token expires. This defeats traditional MFA when session protections are weak.
Privilege escalation after initial access
Once inside a compromised account, attackers abuse authorization gaps, insecure APIs, and role misconfigurations to move laterally, access admin features, extract data, or perform financial abuse.
Most authentication failures are beyond weak passwords and are about scale, automation, broken logic, and inconsistent protection across web, mobile, and APIs.
How to Reduce Risk from Authentication Failures
Reducing authentication risk works best as a set of gates along the attacker journey. First, stop automation at the door with bot defense, adaptive rate limits, and anti-enumeration controls, and apply the same protections to web, mobile, and the underlying authentication APIs. Next, make “getting in” hard even when passwords leak by using phishing-resistant MFA and by hardening the recovery paths attackers love to abuse, like resets and fallback factors.
Then protect what happens after login. Secure sessions by rotating and binding tokens, shortening lifetimes for sensitive actions, and detecting replay or abnormal reuse. Finally, assume some compromises will still happen and catch them early with behavior monitoring and step-up checks. Treat admin access as its own lane with stricter controls. Keep validating all of this with real bot simulations and abuse-case testing so defenses match real attacker behavior.
