# CVE-2026-78551

## Summary

- **CVE ID:** CVE-2026-78551
- **Severity:** HIGH
- **CVSS Score:** 8.8 (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)
- **CWE:** CWE-307, CWE-400
- **Published:** Aug 24, 2026
- **Last Modified:** Aug 24, 2026

## 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.

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 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 Products

- ransomlook — ransomlook (0)

## References

- [CNA](https://github.com/RansomLook/RansomLook/commit/8602740347b0e928ad9fbaf5bc6ff242337dec6b)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.40%
- **EPSS Percentile:** 34.0

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._