CVE-2026-33805

CRITICAL EPSS 24.7%
Published Apr 15, 20262mo ago · Modified Jun 17, 20261w ago
9.0 CVSS 4.0
Critical
Find Similar
Published Apr 15, 2026 2mo ago
Last Modified Jun 17, 2026 1w ago

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.

CVSS Details

Base Score
9.0
Exploitability
—
Impact
—
Vector string
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
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope X

Threat Intelligence

EPSS Exploit Probability
24.7% percentile
Exploit & Patch Status
Public Exploit Known
No Patch Available

Weaknesses 1

CWE-644

Affected Products 2

VendorProductVersionRange
fastifyfastify\/http-proxy* <11.4.4
fastifyreply-from* <12.6.2

References 2

  • cna.openjsf.org https://cna.openjsf.org/security-advisories.html
    Vendor Advisory
  • github.com https://github.com/fastify/fastify-reply-from/security/advisories/GHSA-gwhp-pf74-vj37
    ExploitMitigationVendor Advisory

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.