CVE-2021-39908Network attack vector

Hidden code injection via bidirectional Unicode controls

Published Apr 1, 2022 · Updated Aug 4, 2024

Code injection in affected GitLab versions allows remote authenticated users to conceal malicious project code with Unicode controls. The merge request and source viewers rendered bidirectional control characters without highlighting them, allowing displayed token order to differ from logical source order. Project commit access is required; reviewers can approve code whose visible control flow disguises its executed behavior.

CVSS severity6.5
Medium
EPSS probability1.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Code injection in affected GitLab versions allows remote authenticated users to conceal malicious project code with Unicode controls. The merge request and source viewers rendered bidirectional control characters without highlighting them, allowing displayed token order to differ from logical source order. Project commit access is required; reviewers can approve code whose visible control flow disguises its executed behavior.

The record

CVE
CVE-2021-39908
Published
Apr 1, 2022
Updated
Aug 4, 2024
Vendor
GitLab
Product
GitLab
Classifications
CWE-94, T1027
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 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

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=>=0.8.0, <14.2.6
  2. Affected versionversion=>=14.3, <14.3.4
  3. Affected versionversion=>=14.4, <14.4.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

GitLab · GitLabversion=>=0.8.0, <14.2.6; version=>=14.3, <14.3.4; version=>=14.4, <14.4.1

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N
6.5GitLab Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/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

CWE-94Improper Control of Generation of Code ('Code Injection')
T1027Obfuscated Files or Information

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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