CVE-2023-3900Public exploitNetwork attack vector

Authenticated merge-request denial of service via invalid start_sha

Published Aug 2, 2023 · Updated Nov 20, 2025

Improper input validation in GitLab CE/EE 16.1 through 16.1.2 and 16.2 through 16.2.1 allows remote authenticated users to block Changes tabs. The draft-note endpoint accepts an invalid start_sha in a merge-request discussion position and persists it without verifying that it identifies a valid commit. A project member who can comment on a merge request can leave a malformed thread that prevents all users, including administrators, from loading its Changes tab or deleting the thread.

CVSS severity4.3
Medium
EPSS probability0.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in GitLab CE/EE 16.1 through 16.1.2 and 16.2 through 16.2.1 allows remote authenticated users to block Changes tabs. The draft-note endpoint accepts an invalid start_sha in a merge-request discussion position and persists it without verifying that it identifies a valid commit. A project member who can comment on a merge request can leave a malformed thread that prevents all users, including administrators, from loading its Changes tab or deleting the thread.

The record

CVE
CVE-2023-3900
Published
Aug 2, 2023
Updated
Nov 20, 2025
Vendor
GitLab
Product
GitLab
Classifications
CWE-1287, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 2, 2023CVE publishedPublication date reported by the CVE source.
  2. Nov 20, 2025Record 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=16.1 <16.1.3
  2. Affected versionversion=16.2 <16.2.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

GitLab · GitLabversion=16.1 <16.1.3; version=16.2 <16.2.2

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.3GitLab Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1287Improper Validation of Specified Type of Input
T1499Endpoint Denial of Service

Public exploit references

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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