Findings

Missing retry header

Updated: June 19, 2025

Description

An endpoint is missing the Retry-After header for 429 responses.

Remediation

Ensure the Retry-After header is present in 429 responses. Define proper rate limiting to avoid attackers overloading the API. Part of that involves setting a Retry-After header so well meaning consumers are not polling and potentially exacerbating problems.

Security Frameworks

Satisfying API requests requires resources such as network bandwidth, CPU, memory, and storage. Other resources such as emails/SMS/phone calls or biometrics validation are made available by service providers via API integrations, and paid for per request. Successful attacks can lead to Denial of Service or an increase of operational costs.

Quite often, APIs do not impose any restrictions on the size or number of resources that can be requested by the client/user. Not only can this impact the API server performance, leading to Denial of Service (DoS), but also leaves the door open to authentication flaws such as brute force.

When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.

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Missing rate limit headers
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