CVE-2026-16732
Description
A flaw was found in fastify. When configured with a numeric trustProxy value, an attacker who can directly access the Fastify origin, bypassing the front-facing proxy, can spoof forwarded request fields. This vulnerability allows for host injection in generated URLs, bypasses HTTPS enforcement, and can lead to secure-cookie and Cross-Site Request Forgery (CSRF) origin bypasses, as well as host-based routing and cache poisoning.
Statement
This flaw in fastify allows request spoofing when the trustProxy configuration uses a numeric value and an attacker can directly access the Fastify origin, bypassing the front-facing proxy. This can lead to host injection in generated URLs, HTTPS-enforcement bypass, and secure-cookie/CSRF-origin bypass. Red Hat OpenShift Dev Spaces is affected by this vulnerability.
Mitigation
To mitigate this issue, configure the `trustProxy` setting in fastify to use an IP address, CIDR range, or a custom function that explicitly validates the connecting address. Additionally, ensure that the Fastify origin is only accessible through the trusted proxy chain and not directly exposed to untrusted networks. Consult the fastify documentation for specific configuration details. Reloading or restarting the affected service may be required for changes to take effect.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.1 | N/A | 6.1 |
| Attack Vector | Adjacent Network | N/A | Adjacent Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Changed | N/A | Changed |
| Confidentiality | High | N/A | High |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N
cve.org: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N
Understanding the Weakness (CWE)
Access Control
Technical Impact: Bypass Protection Mechanism
Frequently Asked Questions
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