CVE-2026-33805
@fastify/reply-from vulnerable to connection header abuse enabling stripping of proxy-added headers
- State
- Published
- Severity
- 9.0 Critical
- Published
- Apr 15, 2026
- Updated
- Jul 15, 2026
- Reserved
- Mar 23, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 9.0 Critical | 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 | openjs |
| 3.1 | 7.4 High | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N | redhat-SADP |
Weaknesses
Affected Products
| Product | Versions |
|---|---|
@fastify/reply-from@fastify/reply-from |
|
@fastify/http-proxy@fastify/reply-from |
|
References
- https://github.com/fastify/fastify-reply-from/security/advisories/GHSA-gwhp-pf74-vj37
- https://cna.openjsf.org/security-advisories.html
- https://access.redhat.com/security/cve/CVE-2026-33805vdb-entry
- RHBZ#2458651issue-tracking
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33805.json
- https://access.redhat.com/errata/RHSA-2026:10175vendor-advisory
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