CVE-2026-33805@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.
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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@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
- 8.6 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A: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
- Not given
- NVD analysis
- Modified
- Record last updated
- Jul 15, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
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
- https://cna.openjsf.org/security-advisories.htmlvendor-advisory
- https://github.com/fastify/fastify-reply-from/security/advisories/GHSA-gwhp-pf74-vj37exploit, mitigation, 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.