Critical 9.0Published Apr 15, 2026

CVE-2026-33805@fastify/reply-from vulnerable to connection header abuse enabling stripping of proxy-added headers

Updated under an hour ago (Oct 27, 2026, 9:23 AM ET)

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It affects @fastify/reply-from and 5 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for @fastify/reply-from

Exploited in the last 30 days

@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: 9.0 CRITICAL (v4.0, CNA)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
Weakness (CWE): CWE-644, CWE-444
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: openjs
NVD analysis: Modified
Record last updated: Jul 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

@fastify/reply-from @fastify/reply-from fastify_reply_from:fastify_reply_from (from the name)	before 12.6.2; 12.6.2 not affected	CNA record
@fastify/reply-from @fastify/http-proxy fastify_reply_from:fastify_http_proxy (from the name)	before 11.4.4; 11.4.4 not affected	CNA record
Red Hat Red Hat OpenShift Dev Spaces 3.27 redhat:openshift_devspaces	from 1776795511 not affected	CISA ADP
Red Hat Red Hat OpenShift AI (RHOAI) redhat:openshift_ai	Versions not stated	CISA ADP
fastify fastify/http-proxy fastify:fastify/http-proxy	before 11.4.4	NVD
fastify reply-from fastify:reply-from	before 12.6.2	NVD

References

References

https://github.com/fastify/fastify-reply-from/security/advisories/GHSA-gwhp-pf74-vj37	exploit, mitigation, vendor-advisory
https://cna.openjsf.org/security-advisories.html	vendor-advisory
https://access.redhat.com/errata/RHSA-2026:10175
https://access.redhat.com/security/cve/CVE-2026-33805
https://bugzilla.redhat.com/show_bug.cgi?id=2458651
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33805.json

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.