Description
Monkeytype is a minimalistic and customizable typing test. In 26.26.0 and earlier, the backend rate-limit key generator in backend/src/middlewares/rate-limit.ts uses client-controlled cf-connecting-ip and x-forwarded-for headers before the trust-proxy-derived req.ip value. An unauthenticated attacker can rotate either header to create a new bucket for each request, bypassing rootRateLimiter, badAuthRateLimiter, getKey(), and the getKeyWithUid() fallback used by public endpoints. This permits repeated POST /users/forgotPasswordEmail and verificationEmail requests, mail bombing registered users, consuming Firebase or SMTP quota, evading brute-force protection, and enabling resource exhaustion. Exploitability of cf-connecting-ip depends on deployment topology, but x-forwarded-for and direct-to-origin paths remain affected when those values are not overwritten by a trusted proxy. No fixed version is available as of this review.
Published: 2026-08-20
Score: 7.5 High
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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Remediation

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History

Thu, 20 Aug 2026 16:45:00 +0000

Type Values Removed Values Added
Description Monkeytype is a minimalistic and customizable typing test. In 26.26.0 and earlier, the backend rate-limit key generator in backend/src/middlewares/rate-limit.ts uses client-controlled cf-connecting-ip and x-forwarded-for headers before the trust-proxy-derived req.ip value. An unauthenticated attacker can rotate either header to create a new bucket for each request, bypassing rootRateLimiter, badAuthRateLimiter, getKey(), and the getKeyWithUid() fallback used by public endpoints. This permits repeated POST /users/forgotPasswordEmail and verificationEmail requests, mail bombing registered users, consuming Firebase or SMTP quota, evading brute-force protection, and enabling resource exhaustion. Exploitability of cf-connecting-ip depends on deployment topology, but x-forwarded-for and direct-to-origin paths remain affected when those values are not overwritten by a trusted proxy. No fixed version is available as of this review.
Title Monkeytype: Rate-limit and anti-brute-force controls bypassable via spoofed HTTP headers (forgotPasswordEmail/verificationEmail mail bombing and badAuth bypass)
Weaknesses CWE-290
CWE-307
CWE-644
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-08-20T17:14:13.680Z

Reserved: 2026-08-03T16:00:23.482Z

Link: CVE-2026-69183

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-20T17:19:34.387

Modified: 2026-08-20T17:19:34.387

Link: CVE-2026-69183

cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses