CVE-2021-39939Network attack vector

Manager resource exhaustion via unbounded id output

Published Dec 13, 2021 · Updated Aug 4, 2024

Uncontrolled resource consumption in affected GitLab Runner releases allows remote authenticated users to exhaust runner-manager resources. With the feature flag enabled, the runner executes id inside the job-supplied container and stores its attacker-controlled output in a buffer without a size limit. A user able to submit a Docker-executor job can enable FF_DISABLE_UMASK_FOR_DOCKER_EXECUTOR at job level; the resulting buffer growth interrupts the manager service.

CVSS severity6.5
Medium
EPSS probability0.91%
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 affected GitLab Runner releases allows remote authenticated users to exhaust runner-manager resources. With the feature flag enabled, the runner executes id inside the job-supplied container and stores its attacker-controlled output in a buffer without a size limit. A user able to submit a Docker-executor job can enable FF_DISABLE_UMASK_FOR_DOCKER_EXECUTOR at job level; the resulting buffer growth interrupts the manager service.

The record

CVE
CVE-2021-39939
Published
Dec 13, 2021
Updated
Aug 4, 2024
Vendor
GitLab
Product
GitLab Runner
Classifications
CWE-400, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 13, 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=>=13.7, <14.3.6
  2. Affected versionversion=>=14.4, <14.4.4
  3. Affected versionversion=>=14.5, <14.5.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

GitLab · GitLab Runnerversion=>=13.7, <14.3.6; version=>=14.4, <14.4.4; version=>=14.5, <14.5.2

Published CVSS scores

4.0NIST National Vulnerability DatabaseAV:N/AC:L/Au:S/C:N/I:N/A:P
6.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/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-400Uncontrolled Resource Consumption
T1499Endpoint Denial of Service

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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