CVE-2026-33129

h3 has an observable timing discrepancy in basic auth utils

CVSS 5.9 MEDIUMEPSS 0.3%CWE-208

Vexday Risk Score

13Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 5.9EPSS 0.3%KEV nãoPoC —Nuclei —Metasploit —Patch —

Lifecycle

20 Mar 2026Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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

h3js · h3

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References

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