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CVE-2026-33805

nvd nist
Published: Apr 15, 2026Modified: Jul 15, 2026

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9.0
Vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:L/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
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CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:L/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XShow less
Source: ce714d77-add3-4f53-aff5-83d477b104bb (Secondary)

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.

Affected (2)

Fastify
2 products
Fastify/http Proxy
Reply From
Configuration A
2 vulnerable
Vulnerable SoftwareAffected Versions
Fastify/http Proxy
Before 11.4.4
Reply From
Before 12.6.2

Related CWEs

CWE-444
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.
CWE-644
Improper Neutralization of HTTP Headers for Scripting Syntax
The product does not neutralize or incorrectly neutralizes web scripting syntax in HTTP headers that can be used by web browser components that can process raw headers, such as Flash.

References (7)

Source: ce714d77-add3-4f53-aff5-83d477b104bb
Vendor Advisory
Source: ce714d77-add3-4f53-aff5-83d477b104bb
ExploitMitigationVendor Advisory
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
ExploitMitigationVendor Advisory
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

Timeline

No history available yet.