Vulnerability · Published Mar 20, 2026 · Assigned by GitHub_M

CVE-2026-33129h3 has an observable timing discrepancy in basic auth utils

Medium 5.9

In plain English

A medium-severity security flaw in h3 from h3js. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 26% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.9Medium

Exploit odds (30 days)0.3%top 73.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	h3	2.0.1-rc.9	GHSA-26f5-8h2x-34xh

Affected products (as reported)

Vendor	Product	Versions
h3js	h3	>= 2.0.1-beta.0, < 2.0.1-rc.9

Weakness: CWE-208 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

References

https://github.com/h3js/h3/security/advisories/GHSA-26f5-8h2x-34xh x_refsource_CONFIRM
https://github.com/h3js/h3/pull/1283 x_refsource_MISC
https://github.com/h3js/h3/releases/tag/v2.0.1-rc.9 x_refsource_MISC