{"id":"CVE-2026-78551","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-78551","summary":"RansomLook contains multiple weaknesses in its authentication endpoint that allow an unauthenticated remote attacker to enumerate valid usernames, perform unrestricted password-guessing…","details":"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.","published":"2026-08-24T20:17:23.927","modified":"2026-08-24T20:17:23.927","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[],"fix":{"url":"https://github.com/RansomLook/RansomLook/commit/8602740347b0e928ad9fbaf5bc6ff242337dec6b","label":"RansomLook/RansomLook@8602740"},"references":[{"type":"WEB","url":"https://github.com/RansomLook/RansomLook/commit/8602740347b0e928ad9fbaf5bc6ff242337dec6b"}],"provenance":{"sources":["OSV.dev","NVD","FIRST.org (EPSS)"],"lastVerified":"2026-08-24T20:17:23.927"}}