CVE-2026-33805GHSA-GWHP-PF74-VJ37
@fastify/reply-from vulnerable to connection header abuse enabling stripping of proxy-added headers
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 12.6.2, 11.4.4
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
CISA's decision points: whether it is exploited, whether attacks can be automated, and how much control an attacker gets. Assessed (SSVC 2.0.3).What do these mean? →
- Exploitation: poc
- Automatable: yes
- Technical impact: partial
Summary
@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.
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: poc · Automatable: yes · Technical impact: partial
- Record last updated
Affected versions
- @fastify/reply-from @fastify/reply-from
fixed in 12.6.2
- @fastify/reply-from @fastify/http-proxy
fixed in 11.4.4
- @fastify/reply-fromnpm
fixed in 12.6.2
- @fastify/http-proxynpm
fixed in 11.4.4