CVE-2021-39947

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-06-06 · updated 2026-06-17

Description

In specific circumstances, trace file buffers in GitLab Runner versions up to 14.3.4, 14.4 to 14.4.2, and 14.5 to 14.5.2 would re-use the file descriptor 0 for multiple traces and mix the output of several jobs

Affected products

Gitlab Runner: before 14.3.4; from 14.4.0 before 14.4.2; from 14.5.0 before 14.5.2 — fixed in 14.3.4, 14.4.2, 14.5.2

How to fix

Upgrade to a fixed version: Gitlab Runner 14.3.4, 14.4.2, 14.5.2. Check the vendor advisory for mitigations.

References

https://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-39947.json
https://gitlab.com/gitlab-org/gitlab-runner/-/issues/28732
https://gitlab.com/gitlab-org/cves/-/blob/master/2021/CVE-2021-39947.json
https://gitlab.com/gitlab-org/gitlab-runner/-/issues/28732

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