CVEvulnerability

CVE-2026-33805

9.0 CRITICAL Published 2026-04-15 Modified 2026-10-26 Official page ↗
Status
Modified
Published
2026-04-15
Last modified
2026-10-26
Assigner
ce714d77-add3-4f53-aff5-83d477b104bb
CVSS 4.0 (ce714d77-add3-4f53-aff5-83d477b104bb)
9.0 CRITICAL — 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
CVSS 3.1 ([email protected])
8.6 HIGH — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N
CVSS 3.1 (0b0ca135-0b70-47e7-9f44-1890c2a1c46c)
7.4 HIGH — CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Weaknesses
CWE-444, CWE-644

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 configurations

• fastify fastify\/http-proxy (< 11.4.4) • fastify reply-from (< 12.6.2)

Related

Weakness · CWE (2)

  • CWE-444 Inconsistent Interpretation of HTTP Requests weakness
  • CWE-644 Improper Neutralization of HTTP Headers for Scripting Syntax weakness

References