Mattermost up to 10.11.14/11.4.4/11.5.3/11.6.0 API information disclosure

CVSS Meta Temp Score
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CTI Interest Score
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4.2$0-$5k0.00

Summaryinfo

A vulnerability was found in Mattermost up to 10.11.14/11.4.4/11.5.3/11.6.0. It has been classified as problematic. This vulnerability affects unknown code of the component API. Performing a manipulation results in information disclosure. This vulnerability is identified as CVE-2026-3636. The attack can be initiated remotely. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Mattermost up to 10.11.14/11.4.4/11.5.3/11.6.0. It has been classified as problematic. This affects an unknown code block of the component API. 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 <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to sanitize team member data when returned via API to users without elevated permissions which allows a user without permissions to get data about team members roles via invoking various team API endpoints.. Mattermost Advisory ID: MMSA-2026-00626

The weakness was released by runup. The advisory is shared at mattermost.com. This vulnerability is uniquely identified as CVE-2026-3636 since 03/06/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1592 for this issue.

Upgrading to version 10.11.15, 11.4.5, 11.5.4, 11.6.1 or 11.7.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-1243). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

  • Mattermost Mattermost

Productinfo

Type

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.3
VulDB Meta Temp Score: 4.2

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

CNA Base Score: 4.3
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 10.11.15/11.4.5/11.5.4/11.6.1/11.7.0

Timelineinfo

03/06/2026 CVE reserved
05/22/2026 +76 days Advisory disclosed
05/22/2026 +0 days VulDB entry created
05/25/2026 +3 days VulDB entry last update

Sourcesinfo

Advisory: mattermost.com
Researcher: runup
Status: Confirmed

CVE: CVE-2026-3636 (🔒)
GCVE (CVE): GCVE-0-2026-3636
GCVE (VulDB): GCVE-100-365181
CERT Bund: WID-SEC-2026-1243 - Mattermost: Mehrere Schwachstellen erm&ouml;glichen nicht spezifizierten Angriff

Entryinfo

Created: 05/22/2026 13:51
Updated: 05/25/2026 23:05
Changes: 05/22/2026 13:51 (65), 05/25/2026 23:05 (7)
Complete: 🔍
Cache ID: 216::103

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Discussion

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