CVE-2021-39947Network attack vector

Cross-job trace disclosure via reused file descriptor

Published Jun 6, 2022 · Updated Aug 4, 2024

Information exposure in affected GitLab Runner releases allows remote authenticated users to read trace output from other concurrent jobs. Trace file buffers reuse file descriptor 0 across multiple traces, causing concurrently processed job output to enter the wrong job trace. Exploitation requires low-privileged job access during concurrent execution, and the bounded consequence is cross-job disclosure without reported alteration or interruption.

CVSS severity5.3
Medium
EPSS probability0.84%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information exposure in affected GitLab Runner releases allows remote authenticated users to read trace output from other concurrent jobs. Trace file buffers reuse file descriptor 0 across multiple traces, causing concurrently processed job output to enter the wrong job trace. Exploitation requires low-privileged job access during concurrent execution, and the bounded consequence is cross-job disclosure without reported alteration or interruption.

The record

CVE
CVE-2021-39947
Published
Jun 6, 2022
Updated
Aug 4, 2024
Vendor
GitLab
Product
GitLab Runner
Classifications
Unavailable
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 6, 2022CVE 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=<14.3.4
  2. Affected versionversion=>=14.4, <14.4.2
  3. Affected versionversion=>=14.5, <14.5.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

GitLab · GitLab Runnerversion=<14.3.4; version=>=14.4, <14.4.2; version=>=14.5, <14.5.2

Published CVSS scores

5.3GitLab Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/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 exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

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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