CVE-2025-20621: Github.com/mattermost/mattermost/server/v8 Mattermost Webapp Crash Vulnerability
MODERATECVE-2025-20621 is a MODERATE (CVSS 6.5) mattermost webapp crash vulnerability (CWE-1287: Improper Validation of Specified Type of Input) affecting Github.com/mattermost/mattermost/server/v8 libraries in the Go ecosystem. The issue involves mattermost webapp crash via a crafted post. Remediation is available by upgrading affected packages to version 10.2.1, 10.1.4, 10.0.4, 9.11.6, 8.0.0-20241127161322-25ff7a3779a5.
CVE-2025-20621 at a Glance
Security Impact
CVSS: 6.5
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).
How to Fix CVE-2025-20621
To remediate this vulnerability, upgrade all affected Github.com/mattermost/mattermost/server/v8 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/server/v8 to 10.2.1Upgrade github.com/mattermost/mattermost/server/v8 to 10.1.4Upgrade github.com/mattermost/mattermost/server/v8 to 10.0.4Upgrade github.com/mattermost/mattermost/server/v8 to 9.11.6Upgrade github.com/mattermost/mattermost/server/v8 to 8.0.0-20241127161322-25ff7a3779a5Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for github.com/mattermost/mattermost/server/v8How to Check if You Are Affected
To determine whether your application is affected by CVE-2025-20621, inspect your project dependencies for Github.com/mattermost/mattermost/server/v8:
inspect dependencies for github.com/mattermost/mattermost/server/v8Analyze the terminal output to locate any version of Github.com/mattermost/mattermost/server/v8 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 10.2.1), 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-1287: Improper Validation of Specified Type of Input, where the product receives input that is expected to be of a certain type, but it does not validate or incorrectly validates that the input is actually of the expected type. In Github.com/mattermost/mattermost/server/v8, 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-2025-20621 Affected Github.com/mattermost/mattermost/server/v8 Versions
5 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
github.com/mattermost/mattermost/server/v8
|
Go |
≥ 10.2.0
< 10.2.1
|
10.2.1
|
|
github.com/mattermost/mattermost/server/v8
|
Go |
≥ 10.1.0
< 10.1.4
|
10.1.4
|
|
github.com/mattermost/mattermost/server/v8
|
Go |
≥ 10.0.0
< 10.0.4
|
10.0.4
|
|
github.com/mattermost/mattermost/server/v8
|
Go |
≥ 9.11.0
< 9.11.6
|
9.11.6
|
|
github.com/mattermost/mattermost/server/v8
|
Go |
< 8.0.0-20241127161322-25ff7a3779a5
|
8.0.0-20241127161322-25ff7a3779a5
|
References
Frequently Asked Questions
What is CVE-2025-20621?
Which Github.com/mattermost/mattermost/server/v8 versions are affected?
What version fixes CVE-2025-20621?
Is github.com/mattermost/mattermost/server/v8 affected?
What is the CVSS score of CVE-2025-20621?
What CWE is associated with CVE-2025-20621?
How can I check Go dependencies for CVE-2025-20621?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-w6xh-c82w-h997",
"modified" : "2025-01-16T23:09:09Z",
"published" : "2025-01-16T21:30:58Z",
"aliases" : [ "CVE-2025-20621" ],
"summary" : "Mattermost webapp crash via a crafted post",
"details" : "Mattermost versions 10.2.x <= 10.2.0, 9.11.x <= 9.11.5, 10.0.x <= 10.0.3, 10.1.x <= 10.1.3 fail to properly handle posts with attachments containing fields that cannot be cast to a String, which allows an attacker to cause the webapp to crash via creating and sending such a post to a channel.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "10.2.0"
}, {
"fixed" : "10.2.1"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "10.1.0"
}, {
"fixed" : "10.1.4"
} ]
} ],
"database_specific" : {
"last_known_affected_version_range" : "<= 10.1.3"
}
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "10.0.0"
}, {
"fixed" : "10.0.4"
} ]
} ],
"database_specific" : {
"last_known_affected_version_range" : "<= 10.0.3"
}
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "9.11.0"
}, {
"fixed" : "9.11.6"
} ]
} ],
"database_specific" : {
"last_known_affected_version_range" : "<= 9.11.5"
}
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "8.0.0-20241127161322-25ff7a3779a5"
} ]
} ]
} ],
"references" : [ {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2025-20621"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/mattermost/mattermost"
}, {
"type" : "WEB",
"url" : "https://mattermost.com/security-updates"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-1287" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2025-01-16T23:09:09Z",
"nvd_published_at" : "2025-01-16T19:15:29Z"
}
}