CVE-2021-22177Public exploitNetwork attack vector

Authenticated service interruption via unbounded SSH input

Published Apr 1, 2021 · Updated Aug 3, 2024

Uncontrolled resource consumption in GitLab Shell allows remote authenticated users to interrupt GitLab service through SSH input. The 2fa_recovery_codes confirmation path calls fmt.Fscanln on the client stream without limiting input size, retaining attacker-supplied data in answer while consuming CPU and memory. A valid GitLab SSH key is required, and a sustained oversized response can exhaust server resources and degrade GitLab Shell availability.

CVSS severity4.3
Medium
EPSS probability1.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in GitLab Shell allows remote authenticated users to interrupt GitLab service through SSH input. The 2fa_recovery_codes confirmation path calls fmt.Fscanln on the client stream without limiting input size, retaining attacker-supplied data in answer while consuming CPU and memory. A valid GitLab SSH key is required, and a sustained oversized response can exhaust server resources and degrade GitLab Shell availability.

The record

CVE
CVE-2021-22177
Published
Apr 1, 2021
Updated
Aug 3, 2024
Vendor
GitLab
Product
GitLab
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 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

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=>=12.6, <13.6.7
  2. Affected versionversion=>=13.7, <13.7.7
  3. Affected versionversion=>=13.8, <13.8.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

GitLab · GitLabversion=>=12.6, <13.6.7; version=>=13.7, <13.7.7; version=>=13.8, <13.8.4

Published CVSS scores

4.0NIST NVDAV:N/AC:L/Au:S/C:N/I:N/A:P
4.3GitLab Inc.CVSS:3.1/AV:N/AC:L/PR:L/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.

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-400Uncontrolled Resource Consumption
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

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Your stack

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