Vulnerabilities in pkg:golang/github.com/mattermost/mattermost-plugin-msteams
PACKAGECVE-2026-21388 is a LOW (CVSS 3.7) mattermost ms teams plugin doesn't vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) affecting Github.com/mattermost/mattermost plugin msteams libraries in the Go ecosystem. The issue involves mattermost ms teams plugin doesn't limit the request body size on the /lifecycle webhook endpoint. Remediation is available by upgrading affected packages to version 1.15.1-0.20260213190728-6fe4d295592e.
pkg:golang/github.com/mattermost/mattermost-plugin-msteams
Vulnerability advisories affecting package pkg:golang/github.com/mattermost/mattermost-plugin-msteams. Select an advisory below to view technical details or fixes.
| Advisory ID | CVE / NVD | Severity | Summary |
|---|---|---|---|
| GHSA-x274-8qfc-hrgf | CVE-2026-21388 | LOW | Mattermost MS Teams plugin doesn't limit the request body size on the /lifecycle webhook endpoint |
| GHSA-5rfv-h47g-xj42 | CVE-2026-24661 | MODERATE | Mattermost MS Teams plugin doesn't limit the request body size on the /changes webhook endpoint |
| GHSA-4ppj-6chv-5pgc | CVE-2026-2476 | HIGH | Mattermost Microsoft Teams Plugin fails to properly mask sensitive configuration values |
| GHSA-2j87-p623-8cc2 | CVE-2025-27936 | MODERATE | Mattermost vulnerable to Observable Timing Discrepancy |
CVE-2026-21388 at a Glance
Security Impact
CVSS: 3.7
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L).
How to Fix CVE-2026-21388
To remediate this vulnerability, upgrade all affected Github.com/mattermost/mattermost plugin msteams dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
Upgrade github.com/mattermost/mattermost-plugin-msteams to 1.15.1-0.20260213190728-6fe4d295592eRun the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for github.com/mattermost/mattermost-plugin-msteamsHow to Check if You Are Affected
To determine whether your application is affected by CVE-2026-21388, inspect your project dependencies for Github.com/mattermost/mattermost plugin msteams:
inspect dependencies for github.com/mattermost/mattermost-plugin-msteamsAnalyze the terminal output to locate any version of Github.com/mattermost/mattermost plugin msteams in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.15.1-0.20260213190728-6fe4d295592e), your application is affected.
Note: Verify declared build manifests and deployed runtime container environments.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-770: Allocation of Resources Without Limits or Throttling, where the product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. In Github.com/mattermost/mattermost plugin msteams, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-21388 Affected Github.com/mattermost/mattermost plugin msteams Versions
1 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
github.com/mattermost/mattermost-plugin-msteams
|
Go |
< 1.15.1-0.20260213190728-6fe4d295592e
|
1.15.1-0.20260213190728-6fe4d295592e
|
References
Frequently Asked Questions
What is CVE-2026-21388?
Which Github.com/mattermost/mattermost plugin msteams versions are affected?
What version fixes CVE-2026-21388?
Is github.com/mattermost/mattermost-plugin-msteams affected?
What is the CVSS score of CVE-2026-21388?
What CWE is associated with CVE-2026-21388?
How can I check Go dependencies for CVE-2026-21388?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-x274-8qfc-hrgf",
"modified" : "2026-04-29T20:39:22Z",
"published" : "2026-04-09T12:31:11Z",
"aliases" : [ "CVE-2026-21388" ],
"summary" : "Mattermost MS Teams plugin doesn't limit the request body size on the /lifecycle webhook endpoint ",
"details" : "Mattermost Plugins versions <=2.3.1 fail to limit the request body size on the {{/lifecycle}} webhook endpoint which allows an authenticated attacker to cause memory exhaustion and denial of service via sending an oversized JSON payload. Mattermost Advisory ID: MMSA-2026-00610.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost-plugin-msteams"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "1.15.1-0.20260213190728-6fe4d295592e"
} ]
} ]
} ],
"references" : [ {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-21388"
}, {
"type" : "WEB",
"url" : "https://github.com/mattermost/mattermost-plugin-msteams/commit/6fe4d295592ecc8767d67e69286cbeec01be3210"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/mattermost/mattermost-plugin-msteams"
}, {
"type" : "WEB",
"url" : "https://github.com/mattermost/mattermost-plugin-msteams/releases/tag/v2.3.2"
}, {
"type" : "WEB",
"url" : "https://mattermost.com/security-updates"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-770" ],
"severity" : "LOW",
"github_reviewed" : true,
"github_reviewed_at" : "2026-04-29T20:39:22Z",
"nvd_published_at" : "2026-04-09T11:16:20Z"
}
}