CWE-807: Reliance on Untrusted Inputs in a Security Decision
The product uses a protection mechanism that relies on the existence or values of an input, but the input can be modified by an untrusted actor in a way that bypasses the protection mechanism.
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Overview
Developers may assume that inputs such as cookies, environment variables, and hidden form fields cannot be modified. However, an attacker could change these inputs using customized clients or other attacks. This change might not be detected. When security decisions such as authentication and authorization are made based on the values of these inputs, attackers can bypass the security of the software. Without sufficient encryption, integrity checking, or other mechanism, any input that originates from an outsider cannot be trusted.
Real-world CVEs
61 recorded CVEs are caused by CWE-807 (Reliance on Untrusted Inputs in a Security Decision), including 2 in CISA's KEV (Known Exploited Vulnerabilities) catalog. KEVs are shown first. 30 new CWE-807 CVEs have been recorded so far in 2026 (16 in 2025).