CVE Tools
Sign in

CVE-2026-33805

@fastify/reply-from vulnerable to connection header abuse enabling stripping of proxy-added headers

Published: Apr 15, 2026Updated: Jun 1, 2026 Sources: CVE List NVD BDUCWE-644
NVD MITRE
8.6CVSSHIGH
EPSS Score
0.3%
Top 75.5%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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 Vector Breakdown

AV:NAC:LPR:NUI:NS:CC:NI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:CScope
Changed
Impact
C:NConfidentiality
None
I:HIntegrity
High
A:NAvailability
None
Open in CVSS calculator →

Weaknesses

CWE-644

Affected Products

@fastify/reply-from@fastify/reply-from
Library
OSS Libraries / web-framework
@fastify/http-proxy@fastify/reply-from
Library
OSS Libraries / web-framework
fastify\/http-proxyfastify
Library
OSS Libraries / web-framework
reply-fromfastify
Library
OSS Libraries / web-framework
fastify/http-proxyСообщество свободного программного обеспечения
On-prem
Operating Systems / linux-distro
@fastify/reply-fromoss-projectOSS Libraries
fastifyoss-projectOSS Librariesaka fastify/middie, fastify-multipart
сообщество свободного программного обеспеченияoss-projectOperating Systemsaka сообщество свободного программного обеспечения, fsf
and 1 more affected products View all →

Exploitability

Official Patch Available
Workaround Available

References

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

Timeline

Published
Apr 15, 2026
Last Updated
Jun 1, 2026

Unlock Complete Vulnerability Intelligence

Get the full picture for CVE-2026-33805 and every CVE in our database. Create a free account — no credit card required.

Create Free Account
Plain-language analysis
Impact assessment and exploitation scenario in plain English
Attack graph visualization
Interactive attack path and kill chain mapping
Exploit details & PoC links
ExploitDB, Metasploit, GitHub PoCs with direct links
Nuclei scanner templates
Ready-to-use vulnerability scanner templates
Full remediation guide
Patch instructions, workarounds, and compliance impact
Interactive AI chat
Ask questions about this vulnerability in natural language
Related vulnerabilities
Semantically similar CVEs and attack patterns
REST API & MCP access
Integrate vulnerability data into your workflows