CVE-2026-33805

April 15, 2026, 2:16 p.m.

9.0
Critical

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.

Product(s) Impacted

Vendor Product Versions
Fastify
  • Reply-from
  • Http-proxy
  • 12.6.1
  • 11.4.3

Weaknesses

Common security weaknesses mapped to this vulnerability.

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.

*CPE(s)

Affected systems and software identified for this CVE.

Type Vendor Product Version Update Edition Language Software Edition Target Software Target Hardware Other Information
a fastify reply-from 12.6.1 / / / / / / /
a fastify http-proxy 11.4.3 / / / / / / /

References

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

Tags

CWE-644
ce714d77-add3-4f53-aff5-83d477b104bb
2026-04-15
CVE-2026-33805

CVSS Score

9.0 / 10

CVSS Data - 4.0

  • Attack Vector: NETWORK
  • Attack Complexity: LOW
  • Attack Requirements: PRESENT
  • Privileges Required: NONE
  • User Interaction: NONE
  • Scope:
  • Confidentiality Impact: NONE
  • Integrity Impact: HIGH
  • Availability Impact: NONE
  • Exploit Maturity: NOT_DEFINED

    • 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

    View Vector String

Timeline

Published: April 15, 2026, 11:16 a.m.
Last Modified: April 15, 2026, 2:16 p.m.

Status : Received

CVE has been recently published to the CVE List and has been received by the NVD.

More info

Source

ce714d77-add3-4f53-aff5-83d477b104bb

*Disclaimer: Some vulnerabilities do not have an associated CPE. To enhance the data, we use AI to infer CPEs based on CVE details. This is an automated process and might not always be accurate.