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CVE-2021-39947

25
FAUCET Score

CVE-2021-39947 affects GitLab Runner versions up to 14.3.4, 14.4 to 14.4.2, and 14.5 to 14.5.2, where trace file buffers could reuse file descriptor 0, leading to mixed output from multiple jobs. This vulnerability has a high severity CVSS score of 7.5, indicating a network-exploitable issue with low attack complexity that could lead to high integrity impact without user interaction. While there is no known active exploitation or public exploit code (Metasploit, Nuclei, ExploitDB), it has received some community discussion and media coverage, including a GitLab security advisory.

Impacted Technologies

VendorProductVersion(s)CPE
< 14.3.4CPE matchmatch criteria
cpe:2.3:a:gitlab:gitlab_runner:*:*:*:*:*:*:*:*
>= 14.4.0, < 14.4.2CPE matchmatch criteria
cpe:2.3:a:gitlab:gitlab_runner:*:*:*:*:*:*:*:*
>= 14.5.0, < 14.5.2CPE matchmatch criteria
cpe:2.3:a:gitlab:gitlab_runner:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.3MEDIUM

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
NONE
Exploitability Score
1.6
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.79%
Probability of exploitation in next 30 days
EPSS Percentile
52.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0079 is in the 28th percentile among its peer group of 51,553 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

gitlab.com / gitlab-org/cves/-/blob/master/2021/CVE-2021-39947.json
PatchThird Party Advisory
gitlab.com / gitlab-org/gitlab-runner/-/issues/28732
Broken Link