Home

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.

PUBLISHED Reserved 2026-03-23 | Published 2026-04-15 | Updated 2026-04-15 | Assigner openjs




CRITICAL: 9.0CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:L/SI:H/SA:N

Problem types

CWE-644: Improper Neutralization of HTTP Headers for Scripting Syntax

Product status

Default status
unaffected

Any version before 12.6.2
affected

12.6.2 (semver)
unaffected

Default status
unaffected

Any version before 11.4.4
affected

11.4.4 (semver)
unaffected

Credits

FredKSchott reporter

mcollina remediation developer

UlisesGascon remediation reviewer

climba03003 remediation reviewer

References

github.com/...y-from/security/advisories/GHSA-gwhp-pf74-vj37 exploit

github.com/...y-from/security/advisories/GHSA-gwhp-pf74-vj37

cna.openjsf.org/security-advisories.html

cve.org (CVE-2026-33805)

nvd.nist.gov (CVE-2026-33805)

Download JSON