Vulnerability-Lookup

CVE-2026-33129 (GCVE-0-2026-33129)

Vulnerability from cvelistv5 – Published: 2026-03-20 09:41 – Updated: 2026-03-20 19:33

Title

h3 has an observable timing discrepancy in basic auth utils

Summary

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.

Severity

5.9 (Medium)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-03-20 19:33 UTC

CWE

CWE-208 - Observable Timing Discrepancy

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7771 records in the last 180 days details

References

3 references

URL	Tags
https://github.com/h3js/h3/security/advisories/GH…	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

Impacted products

1 product

Vendor	Product	Version	CPE status
h3js	h3	Affected: >= 2.0.1-beta.0, < 2.0.1-rc.9	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-33129

Vulnerability from fkie_nvd - Published: 2026-03-20 10:16 - Updated: 2026-06-17 10:36

Severity

5.9 (Medium) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
5.9 (Medium) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/h3js/h3/pull/1283	Issue Tracking
security-advisories@github.com	https://github.com/h3js/h3/releases/tag/v2.0.1-rc.9	Patch
security-advisories@github.com	https://github.com/h3js/h3/security/advisories/GHSA-26f5-8h2x-34xh	Exploit, Vendor Advisory

Impacted products

Vendor	Product	Version
h3	h3	2.0.0
h3	h3	2.0.1
h3	h3	2.0.1
h3	h3	2.0.1
h3	h3	2.0.1
h3	h3	2.0.1
h3	h3	2.0.1
h3	h3	2.0.1
h3	h3	2.0.1

JSON

To clipboard

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    },
    {
      "lang": "es",
      "value": "H3 es un framework H(TTP) m\u00ednimo. Las versiones 2.0.1-beta.0 hasta la 2.0.0-rc.8 contienen una vulnerabilidad de canal lateral de tiempo en la funci\u00f3n requireBasicAuth debido al uso de una comparaci\u00f3n de cadenas insegura (!==). Esto permite a un atacante deducir la contrase\u00f1a v\u00e1lida car\u00e1cter por car\u00e1cter midiendo el tiempo de respuesta del servidor, eludiendo eficazmente las protecciones de complejidad de la contrase\u00f1a. Este problema est\u00e1 solucionado en la versi\u00f3n 2.0.1-rc.9."
    }
  ],
  "id": "CVE-2026-33129",
  "lastModified": "2026-06-17T10:36:59.780",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.9,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      },
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.9,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-33129",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-03-20T19:33:14.795855Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-03-20T10:16:19.317",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Issue Tracking"
      ],
      "url": "https://github.com/h3js/h3/pull/1283"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/h3js/h3/releases/tag/v2.0.1-rc.9"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/h3js/h3/security/advisories/GHSA-26f5-8h2x-34xh"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-208"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-26F5-8H2X-34XH

Vulnerability from github – Published: 2026-03-18 16:17 – Updated: 2026-03-20 21:27

Summary

h3 has an observable timing discrepancy in basic auth utils

Details

Summary

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.

Details

The vulnerability is located in the requireBasicAuth function. The code performs a standard string comparison between the user-provided password and the expected password:

if (opts.password && password !== opts.password) {
  throw autheFailed(event, opts?.realm);
}

In V8 (and most runtime environments), the !== operator is optimized to "fail fast." It stops execution and returns false as soon as it encounters the first mismatched byte. * If the first character is wrong, it returns immediately. * If the first character is correct but the second is wrong, it takes slightly longer.

By statistically analyzing these minute timing differences over many requests, an attacker can determine the correct password one character at a time.

PoC

This vulnerability is exploitable in real-world scenarios without direct access to the server machine.

To reproduce this, an attacker can send two packets (or bursts of packets) at the exact same time: 1. Packet A: Contains a password that is known to be incorrect starting at the first character (e.g., AAAA...). 2. Packet B: Contains a password where the first character is a guess (e.g., B...).

By measuring the time-to-first-byte (TTFB) or total response time of these concurrent requests, the attacker can filter out network jitter. If Packet B takes consistently longer to return than Packet A, the first character is confirmed as correct. This process is repeated for the second character, and so on. Tests confirm this timing difference is statistically consistent enough to recover credentials remotely.

Impact

This vulnerability allows remote attackers to recover passwords. While network jitter makes this difficult over the internet, it is highly effective in local networks or cloud environments where the attacker is co-located. It reduces the complexity of cracking a password from exponential (guessing the whole string) to linear (guessing one char at a time).

Severity

5.9 (Medium)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.0.0-rc.8"
      },
      "package": {
        "ecosystem": "npm",
        "name": "h3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0-beta.0"
            },
            {
              "fixed": "2.0.1-rc.9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-33129"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-208"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-18T16:17:58Z",
    "nvd_published_at": "2026-03-20T10:16:19Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\nA 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\u0027s response time, effectively bypassing password complexity protections.\n\n### Details\nThe vulnerability is located in the `requireBasicAuth` function. The code performs a standard string comparison between the user-provided password and the expected password:\n\n~~~typescript\nif (opts.password \u0026\u0026 password !== opts.password) {\n  throw autheFailed(event, opts?.realm);\n}\n~~~\n\nIn V8 (and most runtime environments), the `!==` operator is optimized to \"fail fast.\" It stops execution and returns `false` as soon as it encounters the first mismatched byte.\n* If the first character is wrong, it returns immediately.\n* If the first character is correct but the second is wrong, it takes slightly longer.\n\nBy statistically analyzing these minute timing differences over many requests, an attacker can determine the correct password one character at a time.\n\n### PoC\nThis vulnerability is exploitable in real-world scenarios without direct access to the server machine.\n\nTo reproduce this, an attacker can send two packets (or bursts of packets) at the exact same time:\n1.  **Packet A:** Contains a password that is known to be incorrect starting at the first character (e.g., `AAAA...`).\n2.  **Packet B:** Contains a password where the first character is a guess (e.g., `B...`).\n\nBy measuring the time-to-first-byte (TTFB) or total response time of these concurrent requests, the attacker can filter out network jitter. If Packet B takes consistently longer to return than Packet A, the first character is confirmed as correct. This process is repeated for the second character, and so on. Tests confirm this timing difference is statistically consistent enough to recover credentials remotely.\n\n### Impact\n\nThis vulnerability allows remote attackers to recover passwords. While network jitter makes this difficult over the internet, it is highly effective in local networks or cloud environments where the attacker is co-located. It reduces the complexity of cracking a password from exponential (guessing the whole string) to linear (guessing one char at a time).",
  "id": "GHSA-26f5-8h2x-34xh",
  "modified": "2026-03-20T21:27:48Z",
  "published": "2026-03-18T16:17:58Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/h3js/h3/security/advisories/GHSA-26f5-8h2x-34xh"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33129"
    },
    {
      "type": "WEB",
      "url": "https://github.com/h3js/h3/pull/1283"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/h3js/h3"
    },
    {
      "type": "WEB",
      "url": "https://github.com/h3js/h3/releases/tag/v2.0.1-rc.9"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "h3 has an observable timing discrepancy in basic auth utils"
}

Sightings

Author	Source	Type	Date	Other

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Confirmed: The vulnerability has been validated from an analyst's perspective.
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Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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CVE-2026-33129 (GCVE-0-2026-33129)

FKIE_CVE-2026-33129

GHSA-26F5-8H2X-34XH

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