← Vulnerability feed

Vulnerability record · CVE-2026-33490 · published 26 March 2026

CVE-2026-33490: H3 vulnerability

HH3 · H3

H3 is a minimal H(TTP) framework. In versions 2.0.0-0 through 2.0.1-rc.16, the `mount()` method in h3 uses a simple `startsWith()` check to determine whether incoming requests fall under a mounted sub-application's path prefix. Because this check does not verify a path segment boundary (i.e., that the next character after the base is `/` or end-of-string), middleware registered on a mount like `/admin` will also execute for unrelated routes such as `/admin-public`, `/administrator`, or `/adminstuff`. This allows an attacker to trigger context-setting middleware on paths it was never intended to cover, potentially polluting request context with unintended privilege flags. Version 2.0.2-rc.17 contains a patch.

5.3 CVSS 3.1 Medium EPSS 0.28% · top 81.4% CWE-706 · CWE-706
5.3CVSS 3.1 base score
0.28%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

H3 is a minimal H(TTP) framework. In versions 2.0.0-0 through 2.0.1-rc.16, the `mount()` method in h3 uses a simple `startsWith()` check to determine whether incoming requests fall under a mounted sub-application's path prefix. Because this check does not verify a path segment boundary (i.e., that the next character after the base is `/` or end-of-string), middleware registered on a mount like `/admin` will also execute for unrelated routes such as `/admin-public`, `/administrator`, or `/adminstuff`. This allows an attacker to trigger context-setting middleware on paths it was never intended to cover, potentially polluting request context with unintended privilege flags. Version 2.0.2-rc.17 contains a patch.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/h3js/h3/security/advisories/GHSA-2j6q-whv2-gh6w ExploitMitigationVendor Advisory
https://github.com/h3js/h3/security/advisories/GHSA-2j6q-whv2-gh6w ExploitMitigationVendor Advisory

Track CVE-2026-33490 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2026-33128H3 vulnerabilityH3 is a minimal H(TTP) framework. In versions prior to 1.15.6 and between 2.0.0 through 2.0.1-rc.14, createEventStream is vulnerable to Server-Sent E…EPSS 0.69%9.8CVE-2026-23527H3 http request smuggling vulnerabilityH3 is a minimal H(TTP) framework built for high performance and portability. Prior to 1.15.5, there is a critical HTTP Request Smuggling vulnerabilit…EPSS 0.64%9.1CVE-2026-33131H3 authentication bypass by spoofing vulnerabilityH3 is a minimal H(TTP) framework. Versions 2.0.0-0 through 2.0.1-rc.14 contain a Host header spoofing vulnerability in the NodeRequestUrl (which exte…EPSS 0.44%5.9CVE-2026-33129H3 vulnerabilityH3 is a minimal H(TTP) framework. Versions 2.0.1-beta.0 through 2.0.0-rc.8 contain a Timing Side-Channel vulnerability in the requireBasicAuth functi…EPSS 0.45%9.8CVE-2025-24813Apache Tomcat Default Servlet path equivalence enables RCE and file disclosureApache Tomcat mishandles path equivalence for names containing an internal dot, letting a remote unauthenticated attacker write files through the Def…KEVEPSS 100%analysed9.8CVE-2021-40539Zoho ManageEngine ADSelfService Plus REST API auth bypass to RCEZoho ManageEngine ADSelfService Plus version 6113 and prior contains an authentication bypass in its REST API that leads to remote code execution. Be…KEVEPSS 99%analysed9.8CVE-2020-15505MobileIron Core, Connector, Sentry and RDB remote code executionMobileIron Core, Enterprise Connector, Sentry and Monitor and Reporting Database contain a remote code execution flaw reachable over the network with…KEVEPSS 100%analysed

Source: NIST National Vulnerability Database (record CVE-2026-33490), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.