# JWT signature, issuer, audience, or token-purpose validation failure

A service accepts token claims without the required signature or trusted issuer/key validation.

**Candidate CWE:** [CWE-347](https://cwe.mitre.org/data/definitions/347.html) · [CWE-287](https://cwe.mitre.org/data/definitions/287.html)

## Test hypothesis

Compare the normal controlled token with one invalid signature. Separately use validly signed lab fixtures for a wrong issuer, audience, expiry or token purpose. Change one condition at a time; read the same harmless protected resource. Trace configured algorithm/key trust and purpose-specific validation when source is available.

## Evidence required

Show which invalid condition was accepted and the resulting synthetic identity/capability. Use CWE-347 for signature verification failures; select the actual authentication/trust weakness for semantic validation errors instead of labelling every JWT bug broken cryptography. Redact live credentials.

## Rule out false positives

Base64-decoding claims, accepting a valid token for its intended audience, or displaying untrusted claims without granting access is insufficient.

## Playbook and command references

- [Authentication, recovery, federation, and session lifecycle](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/modules/identity-session.html) — Test registration, recovery, identity changes, invitations, SSO enforcement, and deprovisioning as one account state machine.
- [OAuth, OIDC, and SAML: transaction binding and token trust](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/modules/federation-token-trust.html) — Separate browser transaction binding, issuer trust, token purpose, and identity linking using controlled federation fixtures.

[Find the associated command snippets](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/commands.html?q=Authentication%2C%20recovery%2C%20federation%2C%20and%20session%20lifecycle)

## Referenced by these target playbooks

[Web & API](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/web-api.html) · [OSS & self-hosted](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/oss.html) · [Mobile](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/mobile.html) · [Desktop & extensions](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/desktop.html) · [Cloud & containers](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/cloud.html) · [AI, agents & MCP](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/ai.html)

## Report checklist

- [ ] Capture the affected version, configuration, identities, and object ownership.
- [ ] Preserve a valid baseline and a negative control.
- [ ] Reproduce the forbidden data access, action, or state change on controlled fixtures.
- [ ] Explain the intended security rule and why the observed behavior violates it.
- [ ] State prerequisites, uncertainty, cleanup, and the smallest demonstrated impact.

## Conditional ATT&CK mapping

No direct ATT&CK mapping selected. Record the weakness and demonstrated impact without forcing an adversary-behavior classification. See the [mapping guide](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/attack.html).

## Primary references

- [RFC 8725 JWT Best Current Practices](https://www.rfc-editor.org/rfc/rfc8725.html)
- [OpenID Connect Core incorporating errata set 2](https://openid.net/specs/openid-connect-core-1_0.html)

[Back to the complete vulnerability catalog](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/vulnerabilities.html)