Note Mark: Username Enumeration via Login Endpoint Timing Side-Channel

{
  "id": "d33c5ed8fc1f9c3d5e739958c7819183a1d568d8d95eb7417c656a68579f020d",
  "url": "https://osv.dev/vulnerability/CVE-2026-40263",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Note Mark: Username Enumeration via Login Endpoint Timing Side-Channel",
    "summary": "Note Mark is an open-source note-taking application. In versions 0.19.1 and prior, the login endpoint performs bcrypt password verification only when the supplied username exists, returning immediately for nonexistent usernames. This timing discrepancy allows unauthenticated attackers to enumerate valid usernames by measuring response times, enabling targeted credential attacks. This issue has been fixed in version 0.19.2.",
    "evidence": "osv:CVE-2026-40263",
    "products": [],
    "severity": "low",
    "structured": {
      "id": "CVE-2026-40263",
      "aliases": [
        "CVE-2026-40263",
        "GHSA-w6m9-39cv-2fwp",
        "GO-2026-5696"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/enchant97/note-mark",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "9f627bbb0cccebf872ec4b450ba2cd1d59ba9697"
                },
                {
                  "fixed": "cf4c6f6acf70b569d80396d323b067c00d45c034"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "0.19.2"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "cf4c6f6acf70b569d80396d323b067c00d45c034"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v0.19.1",
            "v0.19.0",
            "v0.18.0",
            "v0.17.1",
            "v0.17.0",
            "v0.16.3",
            "v0.16.2",
            "v0.16.1",
            "v0.16.0",
            "v0.15.4",
            "v0.15.3",
            "v0.15.2",
            "v0.15.1",
            "v0.15.0",
            "v0.14.1",
            "v0.14.0",
            "v0.13.1",
            "v0.13.0",
            "v0.12.2",
            "v0.12.1",
            "v0.12.0",
            "v0.11.1",
            "v0.11.0",
            "v0.10.0",
            "v0.9.0",
            "v0.8.0",
            "v0.7.0",
            "v0.6.0",
            "v0.6.0-alpha.4",
            "v0.6.0-alpha.3",
            "v0.6.0-alpha.2",
            "v0.6.0-alpha"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-40263.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:36.172054293Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40263.json",
        "https://github.com/enchant97/note-mark/security/advisories/GHSA-w6m9-39cv-2fwp",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-40263",
        "https://github.com/enchant97/note-mark/commit/cf4c6f6acf70b569d80396d323b067c00d45c034"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-208"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40263.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-40263",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 503358,
  "published_at": "2026-04-16T23:53:50.195+00:00"
}