CVE-2026-33804 | fastify middie up to 9.3.1 interpretation conflict

VDB-357926 · CVE-2026-33804 · GCVE-0-2026-33804 FASTIFY MIDDIE UP TO 9.3.1 INTERPRETATION CONFLICT HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 6.4 $0-$5k 3.20+ Summaryinfo A vulnerability, which was classified as problematic, was found in fastify middie up to 9.3.1. This affects an unknown function. Such manipulation leads to interpretation conflict. This vulnerability is documented as CVE-2026-33804. The attack can be executed remotely. There is not any exploit available. You should upgrade the affected component. Detailsinfo A vulnerability was found in fastify middie up to 9.3.1 and classified as problematic. Affected by this issue is some unknown functionality. The manipulation with an unknown input leads to a interpretation conflict vulnerability. Using CWE to declare the problem leads to CWE-436. Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B's state. Impacted is confidentiality, integrity, and availability. CVE summarizes: @fastify/middie versions 9.3.1 and earlier are vulnerable to middleware bypass when the deprecated Fastify ignoreDuplicateSlashes option is enabled. The middleware path matching logic does not account for duplicate slash normalization performed by Fastify's router, allowing requests with duplicate slashes to bypass middleware authentication and authorization checks. This only affects applications using the deprecated ignoreDuplicateSlashes option. Upgrade to @fastify/middie 9.3.2 to fix this issue. There are no workarounds other than disabling the ignoreDuplicateSlashes option. The advisory is available at github.com. This vulnerability is handled as CVE-2026-33804 since 03/23/2026. The exploitation is known to be difficult. The attack may be launched remotely. No form of authentication is required for exploitation. The technical details are unknown and an exploit is not available. Upgrading to version 9.3.2 eliminates this vulnerability. Productinfo Vendor fastify Name middie Version 9.3.0 9.3.1 Website Product: https://github.com/fastify/middie/ CPE 2.3info 🔒 🔒 CPE 2.2info 🔒 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv3info VulDB Meta Base Score: 6.5 VulDB Meta Temp Score: 6.4 VulDB Base Score: 5.6 VulDB Temp Score: 5.4 VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA Base Score: 7.4 CNA Vector (openjs): 🔒 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: Interpretation conflict CWE: CWE-436 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: middie 9.3.2 Timelineinfo 03/23/2026 CVE reserved 04/16/2026 +23 days Advisory disclosed 04/16/2026 +0 days VulDB entry created 04/16/2026 +0 days VulDB entry last update Sourcesinfo Product: github.com Advisory: github.com Status: Confirmed CVE: CVE-2026-33804 (🔒) GCVE (CVE): GCVE-0-2026-33804 GCVE (VulDB): GCVE-100-357926 Entryinfo Created: 04/16/2026 16:47 Changes: 04/16/2026 16:47 (62) Complete: 🔍 Cache ID: 99:BCA:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸