CVE-2026-33805 | fastify reply-from/http-proxy prior 12.6.2 Header rewriteRequestHeaders Connection http headers for scripting syntax

VDB-357705 · CVE-2026-33805 · GCVE-0-2026-33805 FASTIFY REPLY-FROM/HTTP-PROXY PRIOR 12.6.2 HEADER REWRITEREQUESTHEADERS CONNECTION HTTP HEADERS FOR SCRIPTING SYNTAX HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 7.0 $0-$5k 2.93 Summaryinfo A vulnerability was found in fastify reply-from and http-proxy. It has been classified as critical. The impacted element is the function rewriteRequestHeaders of the component Header Handler. Performing a manipulation of the argument Connection results in improper neutralization of http headers for scripting syntax. This vulnerability is known as CVE-2026-33805. Remote exploitation of the attack is possible. No exploit is available. Upgrading the affected component is recommended. Detailsinfo A vulnerability classified as critical has been found in fastify reply-from and http-proxy. This affects the function rewriteRequestHeaders of the component Header Handler. The manipulation of the argument Connection with an unknown input leads to a improper neutralization of http headers for scripting syntax vulnerability. CWE is classifying the issue as CWE-644. The product does not neutralize or incorrectly neutralizes web scripting syntax in HTTP headers that can be used by web browser components that can process raw headers, such as Flash. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is: @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. The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-33805 since 03/23/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are known, but no exploit is available. Upgrading to version 12.6.2 eliminates this vulnerability. Productinfo Type Firewall Software Vendor fastify Name http-proxy reply-from CPE 2.3info 🔒 🔒 CPE 2.2info 🔒 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA CVSS-B Score: 🔒 CNA CVSS-BT Score: 🔒 CNA Vector: 🔒 CVSSv3info VulDB Meta Base Score: 7.3 VulDB Meta Temp Score: 7.0 VulDB Base Score: 7.3 VulDB Temp Score: 7.0 VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv2info Vector Complexity Authentication Confidentiality Integrity Availability Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock VulDB Base Score: 🔒 VulDB Temp Score: 🔒 VulDB Reliability: 🔍 Exploitinginfo Class: Improper neutralization of http headers for scripting syntax CWE: CWE-644 CAPEC: 🔒 ATT&CK: 🔒 Physical: No Local: No Remote: Yes Availability: 🔒 Status: Not defined Price Prediction: 🔍 Current Price Estimation: 🔒 0-Day Unlock Unlock Unlock Unlock Today Unlock Unlock Unlock Unlock Threat Intelligenceinfo Interest: 🔍 Active Actors: 🔍 Active APT Groups: 🔍 Countermeasuresinfo Recommended: Upgrade Status: 🔍 0-Day Time: 🔒 Upgrade: reply-from/http-proxy 12.6.2 Timelineinfo 03/23/2026 CVE reserved 04/15/2026 +22 days Advisory disclosed 04/15/2026 +0 days VulDB entry created 04/15/2026 +0 days VulDB entry last update Sourcesinfo Advisory: github.com Status: Confirmed CVE: CVE-2026-33805 (🔒) GCVE (CVE): GCVE-0-2026-33805 GCVE (VulDB): GCVE-100-357705 Entryinfo Created: 04/15/2026 13:59 Changes: 04/15/2026 13:59 (68) Complete: 🔍 Cache ID: 99:F79:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸