CVE-2023-5226Public exploitNetwork attack vector

Repository content substitution via underscore branch bypass

Published Dec 1, 2023 · Updated Aug 14, 2026

Branch validation bypass in GitLab before 16.4.3, 16.5 through 16.5.2, and 16.6.0 allows remote authenticated users to falsify repository content. The prohibited_branch_checks method rejects a hexadecimal identifier followed by -/ but accepts _/, letting a crafted default branch resolve to different content in the UI and a clone. Exploitation requires project access, permission to create and select the branch, and another user to trust the UI view before retrieving attacker-controlled content.

CVSS severity4.8
Medium
EPSS probability0.55%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Branch validation bypass in GitLab before 16.4.3, 16.5 through 16.5.2, and 16.6.0 allows remote authenticated users to falsify repository content. The prohibited_branch_checks method rejects a hexadecimal identifier followed by -/ but accepts _/, letting a crafted default branch resolve to different content in the UI and a clone. Exploitation requires project access, permission to create and select the branch, and another user to trust the UI view before retrieving attacker-controlled content.

The record

CVE
CVE-2023-5226
Published
Dec 1, 2023
Updated
Aug 14, 2026
Vendor
GitLab
Product
GitLab
Classifications
CWE-94, T1565.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 1, 2023CVE publishedPublication date reported by the CVE source.
  2. Aug 14, 2026Record 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 <16.4.3
  2. Affected versionversion=16.5 <16.5.3
  3. Affected versionversion=16.6 <16.6.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

GitLab · GitLabversion=0 <16.4.3; version=16.5 <16.5.3; version=16.6 <16.6.1

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
4.8GitLab Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:R/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 exploitPublished

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')
T1565.001Data Manipulation: Stored Data Manipulation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo