CVE-2021-3138Public exploitNetwork attack vector

Two-factor authentication bypass via unenforced attempt limit

Published Jan 14, 2021 · Updated Aug 3, 2024

Authentication bypass in Discourse 2.6.0 and earlier and 2.7.0 beta1 allows remote attackers to bypass 2FA on certain forms. The 2FA validation path fails to enforce its intended attempt limit for those form submissions, permitting repeated code guesses; public records do not identify the affected controller or limiter defect. Exploitation requires a valid username and password for a 2FA-enabled account, and success exposes only actions available through the affected forms.

CVSS severity7.5
High
EPSS probability3.07%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Discourse 2.6.0 and earlier and 2.7.0 beta1 allows remote attackers to bypass 2FA on certain forms. The 2FA validation path fails to enforce its intended attempt limit for those form submissions, permitting repeated code guesses; public records do not identify the affected controller or limiter defect. Exploitation requires a valid username and password for a 2FA-enabled account, and success exposes only actions available through the affected forms.

The record

CVE
CVE-2021-3138
Published
Jan 14, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-307, T1110
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 14, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:P/I:N/A:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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.

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

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-307Improper Restriction of Excessive Authentication Attempts
T1110Brute Force

Public exploit references

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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