# Parameter or JSON parser disagreement crosses a security check

Validation or authorization uses one interpretation of a request value while the protected operation uses another.

**Candidate CWE:** [CWE-436](https://cwe.mitre.org/data/definitions/436.html)

## Test hypothesis

With A-readable O1 and B-only O2, capture allowed/denied scalar controls. Send one duplicated parameter or literal repeated JSON name in both orders through the normal local ingress. Trace exactly which value each security and execution layer consumes.

## Evidence required

Preserved raw bytes, parse/type/precedence behavior at each component, O1 being authorized, and O2 being consumed with a forbidden controlled result. Include a consistent-parser or strict-schema negative control.

## Rule out false positives

Duplicate acceptance, last-value parsing, a supported multivalue API, or different error text without a violated permission or input contract is insufficient.

## Playbook and command references

- [Request values: duplicate parameters, parser conflicts and downstream queries](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/modules/request-value-parsing.html) — Trace the value a security layer validates through to the value the application or downstream service actually consumes.
- [Object, function, and property authorization](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/modules/authz-matrix.html) — Turn identities, tenants, objects, roles, and lifecycle transitions into a reproducible permission matrix.

[Find the associated command snippets](https://bug-bounty-field-manual.kmahshooq.chatgpt.site/commands.html?q=Request%20values%3A%20duplicate%20parameters%2C%20parser%20conflicts%20and%20downstream%20queries)

## 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) · [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 8259 JSON object names and numeric interoperability](https://www.rfc-editor.org/rfc/rfc8259.html)
- [OWASP WSTG 4.2 HTTP parameter pollution](https://owasp.org/www-project-web-security-testing-guide/v42/4-Web_Application_Security_Testing/07-Input_Validation_Testing/04-Testing_for_HTTP_Parameter_Pollution)
- [CWE-436 interpretation conflict](https://cwe.mitre.org/data/definitions/436.html)

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