Authentication Bypass

auth CRITICAL

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

How It Works

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications. Instead of cracking passwords through brute force, attackers manipulate the authentication process itself to gain unauthorized entry. This typically occurs through one of several pathways: exploiting hardcoded credentials embedded in source code or configuration files, manipulating parameters in authentication requests to skip verification steps, or leveraging broken session management that fails to properly validate user identity.

The attack flow often begins with reconnaissance to identify authentication endpoints and their underlying logic. Attackers may probe for default administrative credentials that were never changed, test whether certain URL paths bypass login requirements entirely, or intercept and modify authentication tokens to escalate privileges. In multi-step authentication processes, flaws in state management can allow attackers to complete only partial verification steps while still gaining full access.

More sophisticated variants exploit single sign-on (SSO) or OAuth implementations where misconfigurations in trust relationships allow attackers to forge authentication assertions. Parameter tampering—such as changing a "role=user" field to "role=admin" in a request—can trick poorly designed systems into granting elevated access without proper verification.

Impact

Complete account takeover — attackers gain full control of user accounts, including administrative accounts, without knowing legitimate credentials
Unauthorized data access — ability to view, modify, or exfiltrate sensitive information including customer data, financial records, and intellectual property
System-wide compromise — admin-level access enables installation of backdoors, modification of security controls, and complete infrastructure takeover
Lateral movement — bypassed authentication provides a foothold for moving deeper into networks and accessing additional systems
Compliance violations — unauthorized access triggers breach notification requirements and regulatory penalties

Real-World Examples

CrushFTP suffered a critical authentication bypass allowing attackers to access file-sharing functionality without any credentials. The vulnerability enabled direct server-side template injection, leading to remote code execution on affected systems. Attackers actively exploited this in the wild to establish persistent access to enterprise file servers.

Palo Alto's Expedition migration tool contained a flaw permitting attackers to reset administrative credentials without authentication. This allowed complete takeover of the migration environment, potentially exposing network configurations and security policies being transferred between systems.

SolarWinds Web Help Desk (CVE-2024-28987) shipped with hardcoded internal credentials that could not be changed through normal administrative functions. Attackers discovering these credentials gained full administrative access to helpdesk systems containing sensitive organizational information and user data.

Mitigation

Implement multi-factor authentication (MFA) — requires attackers to compromise additional verification factors beyond bypassed primary authentication
Eliminate hardcoded credentials — use secure credential management systems and rotate all default credentials during deployment
Enforce authentication on all endpoints — verify every request requires valid authentication; no "hidden" administrative paths should exist
Implement proper session management — use cryptographically secure session tokens, validate on server-side, enforce timeout policies
Apply principle of least privilege — limit damage by ensuring even authenticated users only access necessary resources
Regular security testing — conduct penetration testing specifically targeting authentication logic and flows

Recent CVEs (33198)

CVE-2017-11823

EPSS 3% CVSS 6.7

MEDIUM POC PATCH This Month

The Microsoft Device Guard on Microsoft Windows 10 Gold, 1511, 1607, and 1703, and Windows Server 2016 allows a security feature bypass by the way it handles Windows PowerShell sessions, aka. Rated medium severity (CVSS 6.7), this vulnerability is low attack complexity. Public exploit code available.

Race Condition Microsoft Authentication Bypass +2

NVD Exploit-DB

CVE-2017-11818

EPSS 2% CVSS 4.5

MEDIUM PATCH This Month

The Microsoft Windows Storage component on Microsoft Windows 8.1, Windows Server 2012 R2, Windows RT 8.1, Windows 10 Gold, 1511, 1607, and 1703, and Windows Server 2016 allows a security feature. Rated medium severity (CVSS 4.5).

Microsoft Authentication Bypass Windows 10 +4

NVD

CVE-2016-5791

EPSS 0% CVSS 9.8

CRITICAL Act Now

An Improper Authentication issue was discovered in JanTek JTC-200, all versions. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Authentication Bypass Jtc 200 Firmware

NVD

CVE-2017-5791

EPSS 64% CVSS 9.8

CRITICAL Emergency

The doFilter method in UrlAccessController in HPE Intelligent Management Center (iMC) PLAT 7.2 E0403P06 allows remote bypass of authentication via unspecified strings in a URI. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Epss exploitation probability 64.3% and no vendor patch available.

Authentication Bypass Intelligent Management Center Plat

NVD

CVE-2017-14003

EPSS 1% CVSS 9.8

CRITICAL Act Now

An Authentication Bypass by Spoofing issue was discovered in LAVA Ether-Serial Link (ESL) running firmware versions 6.01.00/29.03.2007 and prior versions. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Authentication Bypass Ether Serial Link Firmware

NVD

CVE-2017-15235

EPSS 13% CVSS 7.5

HIGH POC THREAT Act Now

The File Manager (gollem) module 3.0.11 in Horde Groupware 5.2.21 allows remote attackers to bypass Horde authentication for file downloads via a crafted fn parameter that corresponds to the exact. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and EPSS exploitation probability 12.7%.

Authentication Bypass Groupware

NVD Exploit-DB

CVE-2017-15211

EPSS 1% CVSS 4.3

MEDIUM PATCH This Month

In Kanboard before 1.0.47, by altering form data, an authenticated user can add an external link to a private project of another user. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable, low attack complexity.