CVE-2021-39890Network attack vector

LDAP 2FA bypass via Basic Authentication

Published Dec 6, 2021 · Updated Aug 4, 2024

Authentication bypass in GitLab 14.1.1 and later allows remote attackers to bypass two-factor authentication for LDAP users and access specific pages via Basic Authentication. The authentication flow accepts Basic Authentication for selected pages without enforcing the LDAP user's second factor, defeating the expected 2FA gate. Exploitation requires a valid LDAP user's credentials; impact is unauthorized access to the exposed pages, with no evidence of broader account takeover or service disruption.

CVSS severity9.8
Critical
EPSS probability1.07%
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 GitLab 14.1.1 and later allows remote attackers to bypass two-factor authentication for LDAP users and access specific pages via Basic Authentication. The authentication flow accepts Basic Authentication for selected pages without enforcing the LDAP user's second factor, defeating the expected 2FA gate. Exploitation requires a valid LDAP user's credentials; impact is unauthorized access to the exposed pages, with no evidence of broader account takeover or service disruption.

The record

CVE
CVE-2021-39890
Published
Dec 6, 2021
Updated
Aug 4, 2024
Vendor
GitLab
Product
GitLab
Classifications
CWE-287, T1078
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=>=14.1.1, <14.1.7
  2. Affected versionversion=>=14.2, <14.2.5
  3. Affected versionversion=>=14.3, <14.3.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

GitLab · GitLabversion=>=14.1.1, <14.1.7; version=>=14.2, <14.2.5; version=>=14.3, <14.3.1

Published CVSS scores

7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
3.1GitLabCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T1078Valid Accounts

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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