WSO2 JWT Authentication Bypass and Account Takeover (CVE-2026-5430)

Affected Vendors

WSO2

Affected Components

Identity Server, API Manager, Identity Server as Key Manager

Published Date

2026-08-06

Executive & SecOps Summary

SECOPS ASSESSMENT

Affected Scope

WSO2 Identity Server, API Manager, and products utilizing WSO2 JWT authentication modules.

Impact

Attackers can bypass authentication using crafted JWTs, leading to full administrative account takeover.

Mitigation

Apply official vendor patches immediately and enforce strict JWT algorithm validation policies.

Affected Products & Version Scope

WSO2 Identity Server, WSO2 API Manager, and WSO2 IS as Key Manager deployments using vulnerable JWT validation logic.

Remediation & Live Workaround Commands

PATCH & WORKAROUND

Immediate Patching: Refer to WSO2-2026-5328 and apply the relevant security update for your product version.
Algorithm Whitelisting: Hardcode the allowed JWT algorithms (e.g., only RS256) in the application configuration to prevent algorithm switching attacks.
Security Monitoring: Monitor authentication logs for JWTs containing alg: "none" or unexpected algorithm transitions in the header.

json

// Conceptual Secure Configuration
{
  "jwt": {
    "allowed_algorithms": ["RS256"],
    "enforce_signature": true
  }
}

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Technical Root Cause & Exploitation Mechanics

The vulnerability arises from improper verification of cryptographic signatures (CWE-347) within the JWT handling logic. The system fails to strictly enforce the configured signing algorithms, allowing an attacker to supply a token signed with an unsupported or weak algorithm (such as 'none' or HMAC substitution). This flaw enables unauthorized access to sensitive security boundaries. Given its inclusion in the CISA KEV catalog and an EPSS score of 0.94, this vulnerability is being actively exploited in the wild and poses a critical risk to organizational identity infrastructure.

Official Vendor Advisories & References

NVD Original English Description

The JWT authentication mechanism accepts tokens signed with algorithms other than those explicitly configured or supported. This allows an attacker to craft a JWT with an unsupported algorithm, which is then incorrectly validated, leading to unauthorized access. Successful exploitation of this vulnerability may result in unauthorized access to the system, including the potential compromise of administrative accounts and full account takeover. The CVSS score is adjusted to 9.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) in single-tenant deployments, reflecting that the impact is contained within a single security authority boundary.

https://security.docs.wso2.com/en/latest/security-announcements/security-advisories/2026/WSO2-2026-5328/

Source: ed10eef1-636d-4fbe-9993-6890dfa878f8 · Vendor Advisory

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-5430

Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0 · US Government Resource

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