CVE-2024-21500Network attack vector

2FA bypass via restartable login attempts

Published Feb 17, 2024 · Updated Dec 5, 2024

Improper login throttling in Greenpau Caddy Security 1.1.23 and earlier allows remote attackers to brute-force 2FA codes. The 2FA verification flow blocks repeated code failures within one attempt, but restarting the full multistep login flow supplies fresh attempts and bypasses that limit. Reachability requires an account using 2FA and automation of the complete login flow; a guessed code grants access as that account.

CVSS severity4.8
Medium
EPSS probability0.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper login throttling in Greenpau Caddy Security 1.1.23 and earlier allows remote attackers to brute-force 2FA codes. The 2FA verification flow blocks repeated code failures within one attempt, but restarting the full multistep login flow supplies fresh attempts and bypasses that limit. Reachability requires an account using 2FA and automation of the complete login flow; a guessed code grants access as that account.

The record

CVE
CVE-2024-21500
Published
Feb 17, 2024
Updated
Dec 5, 2024
Vendor
Greenpau
Product
Caddy Security
Classifications
CWE-307, T1110
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 17, 2024CVE publishedPublication date reported by the CVE source.
  2. Dec 5, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=0 <*

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Greenpau · Caddy Securityversion=0 <*

Published CVSS scores

4.8GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-307Improper Restriction of Excessive Authentication Attempts
T1110Brute Force

Public exploit references

No public exploit references are available in this record.

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

Technologies

Your stack

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Your stack

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