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Vulnerability record · CVE-2026-33129 · published 20 March 2026

CVE-2026-33129: H3 vulnerability

HH3 · H3

H3 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 function due to the use of unsafe string comparison (!==). This allows an attacker to deduce the valid password character-by-character by measuring the server's response time, effectively bypassing password complexity protections. This issue is fixed in version 2.0.1-rc.9.

5.9 CVSS 3.1 Medium EPSS 0.45% · top 63.8% CWE-208 · CWE-208
5.9CVSS 3.1 base score
0.45%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References, 1 tagged exploit
17 Jun 2026Last modified by NVD

Description

H3 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 function due to the use of unsafe string comparison (!==). This allows an attacker to deduce the valid password character-by-character by measuring the server's response time, effectively bypassing password complexity protections. This issue is fixed in version 2.0.1-rc.9.

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

Affected products

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

References

LinkTags
https://github.com/h3js/h3/pull/1283 Issue Tracking
https://github.com/h3js/h3/releases/tag/v2.0.1-rc.9 Patch
https://github.com/h3js/h3/security/advisories/GHSA-26f5-8h2x-34xh ExploitVendor Advisory

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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%5.3CVE-2026-33490H3 vulnerabilityH3 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…EPSS 0.28%

Source: NIST National Vulnerability Database (record CVE-2026-33129), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.