RansomLook Login Endpoint Allows Timing-Based Username Enumeration and Unthrottled Authentication Attempts

{
  "id": "da0991fde3902a9000389a615b8a6d9675ea39eb6997f7aa52845c3335812a8d",
  "url": "https://osv.dev/vulnerability/CVE-2026-78551",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "RansomLook Login Endpoint Allows Timing-Based Username Enumeration and Unthrottled Authentication Attempts",
    "summary": "RansomLook contains multiple weaknesses in its authentication endpoint that allow an unauthenticated remote attacker to enumerate valid usernames, perform unrestricted password-guessing attacks, and potentially exhaust application worker resources. For local authentication, the login implementation previously checked whether a submitted username existed before invoking the password hash verification function. Requests containing a nonexistent username therefore returned significantly faster than requests for valid accounts, for which the computationally expensive password verification routine was executed. A remote attacker could measure these response-time differences to determine which usernames correspond to valid RansomLook accounts. In addition, the /login endpoint did not restrict the number or frequency of failed authentication attempts. An attacker could consequently perform password brute-force, dictionary, password-spraying, or credential-stuffing attacks against known accounts without server-side throttling. For valid usernames, each authentication attempt also invokes the password key-derivation function, which consumes a significant amount of CPU time. A sufficiently high rate of login attempts could therefore occupy the application's synchronous Gunicorn workers and cause a denial of service affecting the entire application. The issue has been addressed by always performing password verification using a randomly generated dummy password hash when the supplied us",
    "evidence": "osv:CVE-2026-78551",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-78551",
      "aliases": [
        "CVE-2026-78551"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/ransomlook/ransomlook",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "8602740347b0e928ad9fbaf5bc6ff242337dec6b"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "last_affected": "2.0.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "fixed": "8602740347b0e928ad9fbaf5bc6ff242337dec6b"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "2.0.0",
            "1.9.0",
            "1.8.0",
            "1.6.0",
            "1.5.0",
            "1.4.0",
            "1.3.0",
            "1.2.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-78551.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:36.076170284Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/78xxx/CVE-2026-78551.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-78551",
        "https://github.com/RansomLook/RansomLook/commit/8602740347b0e928ad9fbaf5bc6ff242337dec6b"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-307",
          "CWE-400"
        ],
        "cna_assigner": "CIRCL",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/78xxx/CVE-2026-78551.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-78551",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 503392,
  "published_at": "2026-08-24T19:20:03.145+00:00"
}