Bug 2458651 (CVE-2026-33805) - CVE-2026-33805 @fastify/reply-from: @fastify/http-proxy: Fastify Reply From and HTTP Proxy: Security bypass via Connection header manipulation
Summary: CVE-2026-33805 @fastify/reply-from: @fastify/http-proxy: Fastify Reply From a...
Keywords:
Status: NEW
Alias: CVE-2026-33805
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-04-15 11:01 UTC by OSIDB Bzimport
Modified: 2026-04-16 21:07 UTC (History)
3 users (show)

Fixed In Version:
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Description OSIDB Bzimport 2026-04-15 11:01:21 UTC 
@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.
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