{"id":"CVE-2026-78551","state":"PUBLISHED","title":"RansomLook Login Endpoint Allows Timing-Based Username Enumeration and Unthrottled Authentication Attempts","description":"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.\n\nFor 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.\n\nIn 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.\n\nThe issue has been addressed by always performing password verification using a randomly generated dummy password hash when the supplied username does not exist, eliminating the username-dependent timing discrepancy. Failed authentication attempts are additionally rate-limited per client IP address using Valkey/Redis, with five failed attempts within five minutes resulting in a one-hour block. The reverse-proxy configuration was also updated so that the application derives the client address from a trusted X-Forwarded-For value that cannot be overridden by a client-supplied header.","publishedAt":"2026-08-24T19:20:03.145Z","updatedAt":"2026-08-24T20:07:41.242Z","severity":{"score":8.8,"label":"High","version":"4.0","vector":"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","source":"CIRCL"},"assigner":"CIRCL","products":["ransomlook ransomlook"],"affected":[{"vendor":"ransomlook","product":"ransomlook","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"2.0.0","versionType":"semver"}]}],"references":["https://github.com/RansomLook/RansomLook/commit/8602740347b0e928ad9fbaf5bc6ff242337dec6b"],"weaknesses":["CWE-307","CWE-400"],"ingestedAt":"2026-10-29T20:13:07.220Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/78xxx/CVE-2026-78551.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-78551","state":"PUBLISHED","datePublished":"2026-08-24T19:20:03.145Z","dateUpdated":"2026-08-24T20:07:41.242Z","assignerShortName":"CIRCL","assignerOrgId":"5a6e4751-2f3f-4070-9419-94fb35b644e8","dateReserved":"2026-08-24T19:19:59.060Z"},"containers":{"cna":{"title":"RansomLook Login Endpoint Allows Timing-Based Username Enumeration and Unthrottled Authentication Attempts","descriptions":[{"lang":"en","value":"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.\n\nFor 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.\n\nIn 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.\n\nThe issue has been addressed by always performing password verification using a randomly generated dummy password hash when the supplied username does not exist, eliminating the username-dependent timing discrepancy. Failed authentication attempts are additionally rate-limited per client IP address using Valkey/Redis, with five failed attempts within five minutes resulting in a one-hour block. The reverse-proxy configuration was also updated so that the application derives the client address from a trusted X-Forwarded-For value that cannot be overridden by a client-supplied header."}],"affected":[{"vendor":"ransomlook","product":"ransomlook","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThanOrEqual":"2.0.0","versionType":"semver"}]}],"references":[{"url":"https://github.com/RansomLook/RansomLook/commit/8602740347b0e928ad9fbaf5bc6ff242337dec6b","tags":["patch"]}],"metrics":[{"cvssV4_0":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":8.8,"baseSeverity":"HIGH","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"NOT_DEFINED","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"LOW","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"NOT_DEFINED"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-307","description":"CWE-307 Improper Restriction of Excessive Authentication Attempts","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-400","description":"CWE-400 Uncontrolled Resource Consumption","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"CIRCL","orgId":"5a6e4751-2f3f-4070-9419-94fb35b644e8","dateUpdated":"2026-08-24T19:20:03.145Z"},"credits":[{"lang":"en","type":"finder","value":"Jeroen Pinoy"},{"lang":"en","type":"remediation developer","value":"Fafner [_KeyZee_]"}],"impacts":[{"capecId":"CAPEC-49","descriptions":[{"lang":"en","value":"CAPEC-49 Password Brute Forcing"}]},{"capecId":"CAPEC-16","descriptions":[{"lang":"en","value":"CAPEC-16 Dictionary-based Password Attack"}]},{"capecId":"CAPEC-565","descriptions":[{"lang":"en","value":"CAPEC-565 Password Spraying"}]},{"capecId":"CAPEC-600","descriptions":[{"lang":"en","value":"CAPEC-600 Credential Stuffing"}]}],"source":{"discovery":"UNKNOWN"},"x_generator":{"engine":"Vulnogram 0.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-24T20:07:33.863606Z","id":"CVE-2026-78551","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-24T20:07:41.242Z"}}]}}}