CVE-2026-33805
8.6 · HIGHOverview
CVE-2026-33805 is a high-severity vulnerability affecting fastify fastify\/http-proxy. It was published on April 15, 2026 and has a CVSS 3.1 base score of 8.6 (HIGH).
This vulnerability has a CVSS 3.1 base score of 8.6, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical 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.
Remediation
Check the references section for vendor advisories and patches from fastify. Update fastify\/http-proxy to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| fastify | fastify\/http-proxy | >= 0, < 11.4.4 | Affected |
| fastify | reply-from | >= 0, < 12.6.2 | Affected |
References
Frequently Asked Questions
What is CVE-2026-33805?
CVE-2026-33805 is a high-severity vulnerability affecting fastify fastify\/http-proxy. It was published on April 15, 2026 and has a CVSS 3.1 base score of 8.6 (HIGH).
How severe is CVE-2026-33805?
This vulnerability has a CVSS 3.1 base score of 8.6, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-33805?
Check the references section for vendor advisories and patches from fastify. Update fastify\/http-proxy to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-33805?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-33805 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
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