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

March 18, 2026 (updated March 20, 2026)

A Timing Side-Channel vulnerability exists 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.

References

github.com/advisories/GHSA-26f5-8h2x-34xh
github.com/h3js/h3
github.com/h3js/h3/pull/1283
github.com/h3js/h3/releases/tag/v2.0.1-rc.9
github.com/h3js/h3/security/advisories/GHSA-26f5-8h2x-34xh
nvd.nist.gov/vuln/detail/CVE-2026-33129

Code Behaviors & Features

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