Mattermost Desktop App up to 5.5.13/6.1.x window.open allocation of resources

CVSS Meta Temp Score
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CTI Interest Score
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5.3$0-$5k0.00

Summaryinfo

A vulnerability, which was classified as problematic, was found in Mattermost Desktop App up to 5.5.13/6.1.x. Affected by this issue is the function window.open. The manipulation results in allocation of resources. This vulnerability is reported as CVE-2026-8683. The attack can be launched remotely. No exploit exists. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Mattermost Desktop App up to 5.5.13/6.1.x. It has been classified as problematic. Affected is the function window.open. The manipulation with an unknown input leads to a allocation of resources vulnerability. CWE is classifying the issue as CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. This is going to have an impact on availability. CVE summarizes:

Mattermost Desktop App versions <=6.1 5.5.13.0 fail to account for attempting to open extremely long URLs in the Mattermost Desktop App which allows a malicious server owner to crash the application via including a script to call window.open on a very large URL. Mattermost Advisory ID: MMSA-2026-00652

The weakness was disclosed by game0v3r. The advisory is shared for download at mattermost.com. This vulnerability is traded as CVE-2026-8683 since 05/15/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1499.

The vulnerability scanner Nessus provides a plugin with the ID 321513 (Mattermost Desktop 5.13.x < 5.13.6 / 6.x < 6.2.0 Multiple Vulnerabilities (MMSA-2026-00651 / MMSA-2026-00652)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.13.6.0 or 6.2.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (321513). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

Vendor

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.4
VulDB Meta Temp Score: 5.3

VulDB Base Score: 4.3
VulDB Temp Score: 4.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 6.5
CNA Vector (Mattermost): 🔒

CVSSv2info

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

Exploitinginfo

Class: Allocation of resources
CWE: CWE-770 / CWE-400 / CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 321513
Nessus Name: Mattermost Desktop 5.13.x < 5.13.6 / 6.x < 6.2.0 Multiple Vulnerabilities (MMSA-2026-00651 / MMSA-2026-00652)

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Desktop App 5.13.6.0/6.2.0

Timelineinfo

05/15/2026 CVE reserved
06/15/2026 +31 days Advisory disclosed
06/15/2026 +0 days VulDB entry created
06/18/2026 +3 days VulDB entry last update

Sourcesinfo

Advisory: mattermost.com
Researcher: game0v3r
Status: Confirmed

CVE: CVE-2026-8683 (🔒)
GCVE (CVE): GCVE-0-2026-8683
GCVE (VulDB): GCVE-100-370932

Entryinfo

Created: 06/15/2026 18:33
Updated: 06/18/2026 21:35
Changes: 06/15/2026 18:33 (65), 06/18/2026 21:35 (2)
Complete: 🔍
Cache ID: 216::103

Once again VulDB remains the best source for vulnerability data.

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