CVE-2026-77561Public exploitNetwork attack vectorHinoki check available

Unauthenticated login denial via global lockdown

Published Sep 21, 2026 · Updated Sep 21, 2026

Improper login throttling in Tinyauth before 5.1.0 allows remote attackers to block valid logins through crafted requests. loginHandler records attacker-chosen nonexistent usernames until RecordLoginAttempt fills its bounded map and lockdownMode sets a global lock checked before individual accounts. Access to POST /api/user/login and 257 distinct identifiers is sufficient; unrelated users then receive HTTP 429 for about 300 seconds by default, while existing sessions remain valid.

CVSS severity5.3
Medium
EPSS probability0.60%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Get started

Summary

What happened

Improper login throttling in Tinyauth before 5.1.0 allows remote attackers to block valid logins through crafted requests. loginHandler records attacker-chosen nonexistent usernames until RecordLoginAttempt fills its bounded map and lockdownMode sets a global lock checked before individual accounts. Access to POST /api/user/login and 257 distinct identifiers is sufficient; unrelated users then receive HTTP 429 for about 300 seconds by default, while existing sessions remain valid.

The record

CVE
CVE-2026-77561
Published
Sep 21, 2026
Updated
Sep 21, 2026
Vendor
Tinyauth
Product
Tinyauth
Classifications
CWE-307, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 5.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Tinyauth · Tinyauthversion=< 5.1.0

Published CVSS scores

5.3GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-307Improper Restriction of Excessive Authentication Attempts
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Get started to see how Hinoki identifies affected software and validates exploitability in your environment.

Get started