CVE-2026-33805

HighCVSS 8.6/10Last modified Jul 15, 2026

Description

@fastify/reply-from v12.6.1 and earlier and @fastify/http-proxy v11.4.3 and earlier process the client's Connection header after the proxy has added its own headers via rewriteRequestHeaders. This allows attackers to retroactively strip proxy-added headers from upstream requests by listing them in the Connection header value. Any header added by the proxy for routing, access control, or security purposes can be selectively removed by a client. @fastify/http-proxy is also affected as it delegates to @fastify/reply-from.

Upgrade to @fastify/reply-from v12.6.2 or @fastify/http-proxy v11.4.4 or later.

Metrics

CVSS 3.1 8.6/10CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

Weakness enumeration

CWE-644 CWE-444

Affected software

No affected versions have been published.

Timeline

Published: Apr 15, 2026
Last modified: Jul 15, 2026
NVD status: Modified

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