Mattermost up to 11.6.x Direct Message information disclosure

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 (≈)
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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.
4.1$0-$5k0.00

Summaryinfo

A vulnerability identified as problematic has been detected in Mattermost up to 10.11.15/10.11.16/11.5.4/11.6.1/11.6.x. This vulnerability affects unknown code of the component Direct Message Handler. Performing a manipulation results in information disclosure. This vulnerability is cataloged as CVE-2026-6046. It is possible to initiate the attack remotely. There is no exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Mattermost up to 10.11.15/10.11.16/11.5.4/11.6.1/11.6.x. This affects some unknown functionality of the component Direct Message Handler. The manipulation with an unknown input leads to a information disclosure vulnerability. CWE is classifying the issue as CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. This is going to have an impact on confidentiality. The summary by CVE is:

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username.. Mattermost Advisory ID: MMSA-2026-00649

The weakness was shared by insomnia1102. It is possible to read the advisory at mattermost.com. This vulnerability is uniquely identified as CVE-2026-6046 since 04/09/2026. The exploitability is told to be difficult. It is possible to initiate the attack remotely. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1592 according to MITRE ATT&CK.

Upgrading to version 10.11.16, 10.11.17, 11.5.5, 11.6.2 or 11.7.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-36502). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.2
VulDB Meta Temp Score: 4.1

VulDB Base Score: 3.1
VulDB Temp Score: 3.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 5.3
CNA Vector (Mattermost): 🔒

CVSSv2info

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

Exploitinginfo

Class: Information disclosure
CWE: CWE-200 / CWE-284 / CWE-266
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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Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Mattermost 10.11.16/10.11.17/11.5.5/11.6.2/11.7.0

Timelineinfo

04/09/2026 CVE reserved
06/12/2026 +64 days Advisory disclosed
06/12/2026 +0 days VulDB entry created
06/12/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: mattermost.com
Researcher: insomnia1102
Status: Confirmed

CVE: CVE-2026-6046 (🔒)
GCVE (CVE): GCVE-0-2026-6046
GCVE (VulDB): GCVE-100-370659
EUVD: 🔒

Entryinfo

Created: 06/12/2026 19:36
Updated: 06/12/2026 22:14
Changes: 06/12/2026 19:36 (65), 06/12/2026 22:14 (1)
Complete: 🔍
Cache ID: 216::103

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

Discussion

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