CVE-2026-33129

h3 has an observable timing discrepancy in basic auth utils

MEDIUM
5.9
CVSS Score
Published: March 20, 2026 at 09:41 AM UTC
Updated: June 17, 2026 at 10:36 AM UTC
2 products affected across 2 vendorsH3H3

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Severity
MEDIUM5.9
Exploit prediction
EPSS 0.3%
SSVC
PoC

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

60%
v < 2.0.1-rc.9
Affected range stops below 2.0.1-rc.9, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (3)

x_refsource_CONFIRMExploitVendor Advisory
Source: cverecord
https://github.com/h3js/h3/security/advisories/GHSA-26f5-8h2x-34xh
x_refsource_MISCIssue Tracking
Source: cverecord
https://github.com/h3js/h3/pull/1283
x_refsource_MISCPatch
Source: cverecord
https://github.com/h3js/h3/releases/tag/v2.0.1-rc.9

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.9MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
HIGH
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-208

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