CWE-441: Unintended Proxy or Intermediary ('Confused Deputy')

The product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere. This causes the product to appear to be the source of the request, leading it to act as a proxy or other intermediary between the upstream component and the external actor.

If an attacker cannot directly contact a target, but the product has access to the target, then the attacker can send a request to the product and have it be forwarded to the target. The request would appear to be coming from the product's system, not the attacker's system. As a result, the attacker can bypass access controls (such as firewalls) or hide the source of malicious requests, since the requests would not be coming directly from the attacker. Since proxy functionality and message-forwarding often serve a legitimate purpose, this issue only becomes a vulnerability when: The product runs with different privileges or on a different system, or otherwise has different levels of access than the upstream component; The attacker is prevented from making the request directly to the target; and The attacker can create a request that the proxy does not explicitly intend to be forwarded on the behalf of the requester. Such a request might point to an unexpected hostname, port number, hardware IP, or service. Or, the request might be sent to an allowed service, but the request could contain disallowed directives, commands, or resources.

Consequences

• Non-Repudiation, Access Control: Gain Privileges or Assume Identity, Hide Activities, Execute Unauthorized Code or Commands

How to prevent it

• Architecture and Design: Enforce the use of strong mutual authentication mechanism between the two parties.
• Architecture and Design: Whenever a product is an intermediary or proxy for transactions between two other components, the proxy core should not drop the identity of the initiator of the transaction. The immutability of the identity of the initiator must be maintained and should be forwarded all the way to the target.

Recent advisories

• GHSA-7hp6-4w63-5g45 — LiteLLM: Privilege Escalation to Proxy Admin via Cross-Domain Reuse of the Salt Key
• GHSA-jmqq-x5g9-9p2w — AsyncHttpClient: Replay to a different host sends the original host request and credentials to the new host
• GHSA-29gx-h2m3-xw44 — Backstage's scaffolder credential handling may allow unintended GitHub authentication fallback
• GHSA-r4gj-5m52-g5wh — Axios: maxRedirects: 0 is not enforced by the fetch adapter, allowing redirect-based SSRF
• GHSA-m8m8-qj5v-23w3 — Axios: Node HTTP adapter prototype-pollution gadget allows request socket hijack via inherited createConnection
• GHSA-2xj6-xx86-cwwc — MCP Atlassian: Arbitrary File Read & Exfiltration (Confused Deputy) in JIRA update_issue
• GHSA-wv8v-v4c5-v75j — MCP Atlassian: MCP HTTP Client Server-Local File Exfiltration via Unvalidated Attachment Upload Path
• GHSA-9gm5-9rfh-m6vx — CoreDNS DoH/DoQ/gRPC bypass UPDATE rejection enforced on UDP/TCP
• CVE-2026-83548 — A Pre-authentication SSRF vulnerability exists in the SMA1000 Appliance Work Place interface due to an unintended alternate access path.
• GHSA-6ww7-3frv-cqxh — NLTK: pathsec SSRF protection can be bypassed when a proxy is configured
• GHSA-x5c9-v98j-722r — 9router /v1 APIs has unauthenticated access via reverse proxy locality collapse
• GHSA-fmh4-wcc4-5jm3 — Better Auth vulnerable to unauthorized invitation acceptance via unverified email match in organization plugin
• GHSA-5g4w-3vw9-478w — Coder's subdomain workspace app routing trusts unauthenticated X-Forwarded-Host header, enabling cross-app data access
• GHSA-hmcr-rmjq-47qr — NocoDB: Server-Side Request Forgery via Spreadsheet Import Endpoint
• GHSA-vjhc-cf4p-72q4 — Fission: Cross-namespace Environment reference in Package allows build-time command execution and SA token exfiltration

All advisories for CWE-441