CVE-2021-22254Public exploitNetwork attack vector

User impersonation via ambiguous SSH argument parsing

Published Aug 20, 2021 · Updated Aug 3, 2024

SSH parsing in GitLab CE/EE 13.1 through 13.12.8, 14.0 through 14.0.6, and 14.1 through 14.1.1 allows remote authenticated users to impersonate users. The GitLab Shell parser checks an unanchored key-ID regex before the username regex, so username-key-2 is treated as SSH key ID 2. Exploitation requires configured SSH certificate authentication, a certificate for a crafted username such as key-2, and an existing victim key ID; access is limited to the victim account's SSH permissions.

CVSS severity3.1
Low
EPSS probability0.87%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

SSH parsing in GitLab CE/EE 13.1 through 13.12.8, 14.0 through 14.0.6, and 14.1 through 14.1.1 allows remote authenticated users to impersonate users. The GitLab Shell parser checks an unanchored key-ID regex before the username regex, so username-key-2 is treated as SSH key ID 2. Exploitation requires configured SSH certificate authentication, a certificate for a crafted username such as key-2, and an existing victim key ID; access is limited to the victim account's SSH permissions.

The record

CVE
CVE-2021-22254
Published
Aug 20, 2021
Updated
Aug 3, 2024
Vendor
GitLab
Product
GitLab
Classifications
CWE-116, T1078, T1021.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 20, 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?

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

  1. Affected versionversion=>=13.1, <13.12.9
  2. Affected versionversion=>=14.0, <14.0.7
  3. Affected versionversion=>=14.1, <14.1.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

GitLab · GitLabversion=>=13.1, <13.12.9; version=>=14.0, <14.0.7; version=>=14.1, <14.1.2

Published CVSS scores

4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
3.1GitLab Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N
3.5NIST NVDAV:N/AC:M/Au:S/C:P/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.

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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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-116Improper Encoding or Escaping of Output
T1078Valid Accounts
T1021.004Remote Services: SSH

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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