CVE WatchJul 15, 2026

CVE-2026-33805

@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 h

CVSS

8.6

High

EPSS

0.4%

p36

KEV

—

Exploit Today

0-100

Published: Apr 15, 2026 · Last modified: Jul 15, 2026 · CWE-644 · CWE-444

EPSS · 30d

0.4%EPSS · 30 days0.4%

2026-06-302026-07-17

Technical 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.

Official references

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