VDB-359027 · CVE-2026-3254 · EUVD-2026-24961

GitLab Community Edition/Enterprise Edition up to 18.11.0 Mermaid Sandbox ui layer

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
3.4	$0-$5k	0.00

Summaryinfo

A vulnerability marked as problematic has been reported in GitLab Community Edition and Enterprise Edition up to 18.11.0. This impacts an unknown function of the component Mermaid Sandbox. The manipulation leads to ui layer. This vulnerability is uniquely identified as CVE-2026-3254. The attack is possible to be carried out remotely. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in GitLab Community Edition and Enterprise Edition up to 18.11.0. It has been rated as problematic. This issue affects an unknown code of the component Mermaid Sandbox. The manipulation with an unknown input leads to a ui layer vulnerability. Using CWE to declare the problem leads to CWE-1021. The web application does not restrict or incorrectly restricts frame objects or UI layers that belong to another application or domain, which can lead to user confusion about which interface the user is interacting with. Impacted is integrity. The summary by CVE is:

GitLab has remediated an issue in GitLab CE/EE affecting all versions from 18.11 before 18.11.1 that under certain conditions could have allowed an authenticated user to load unauthorized content into another user's browser due to improper input validation in the Mermaid sandbox.

The weakness was disclosed by joaxcar. It is possible to read the advisory at hackerone.com. The identification of this vulnerability is CVE-2026-3254 since 02/26/2026. The exploitation is known to be easy. The attack may be initiated remotely. It demands that the victim is doing some kind of user interaction. The technical details are unknown and an exploit is not publicly available.

Upgrading to version 18.11.1 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-24961). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

Bug Tracking Software

Vendor

GitLab

Name

Version

License

open-source

Website

Vendor: https://gitlab.com/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 3.5
VulDB Meta Temp Score: 3.4

VulDB Base Score: 3.5
VulDB Temp Score: 3.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 3.5
CNA Vector (GitLab): 🔒

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Ui layer
CWE: CWE-1021
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Community Edition/Enterprise Edition 18.11.1

Timelineinfo

02/26/2026 CVE reserved
04/22/2026 +54 days Advisory disclosed
04/22/2026 +0 days VulDB entry created
04/22/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: gitlab.com

Advisory: hackerone.com
Researcher: joaxcar
Status: Confirmed

CVE: CVE-2026-3254 (🔒)
GCVE (CVE): GCVE-0-2026-3254
GCVE (VulDB): GCVE-100-359027
EUVD: 🔒

Entryinfo

Created: 04/22/2026 19:03
Updated: 04/22/2026 21:25
Changes: 04/22/2026 19:03 (66), 04/22/2026 21:25 (1)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.