# SAML assertion signature, audience, or response binding failure

The service provider trusts an assertion whose signature or authentication context is not valid for the receiving flow.

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

## Test hypothesis

Use a local IdP/SP with two synthetic accounts. Compare a valid assertion with independently changed signed content, wrong audience/recipient, expiry, one replay, and mismatched InResponseTo where required. Trace which validated signed XML element supplies the consumed identity and attributes.

## Evidence required

Record the accepted identity, trust configuration, validation path, and the one invalid condition that survives. Keep signature failure separate from audience or response-binding failure when assigning a CWE.

## Rule out false positives

Decoding XML, modifying an unsigned irrelevant field, or using an explicitly supported IdP-initiated flow does not prove forgery. A signature check on one element does not establish that the consumed identity came from that element.

## 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.
- [Source review: entry point to protected operation](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/modules/source-dataflow.html) — Trace attacker control and authorization through handlers, services, queues, and sensitive operations; promote only reachable violations of a stated invariant.
- [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) · [Cloud & containers](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/cloud.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

- [OWASP SAML security](https://cheatsheetseries.owasp.org/cheatsheets/SAML_Security_Cheat_Sheet.html)

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