CVE-2017-18889: Github.com/mattermost/mattermost server Mattermost Server Is Vulnerable To Vulnerability

MODERATE
Advisory Identifier: GHSA-jp57-4x34-5v94
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CVSS 4.3
CWE-20
Published
Advisory Summary

CVE-2017-18889 is a MODERATE (CVSS 4.3) mattermost server is vulnerable to vulnerability (CWE-20: Improper Input Validation) affecting Github.com/mattermost/mattermost server libraries in the Go ecosystem. The issue involves mattermost server is vulnerable to webhook and slash command manipulation. Remediation is available by upgrading affected packages to version 4.1.2, 4.2.1, 4.3.0.

CVE-2017-18889 at a Glance

CVE Identifier CVE-2017-18889
GHSA Identifier GHSA-jp57-4x34-5v94
Severity MODERATE
CVSS v3.1 Base Score 4.3
CWE Classification CWE-20: Improper Input Validation
Affected Product Github.com/mattermost/mattermost server
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 4.3

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:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2017-18889

To remediate this vulnerability, upgrade all affected Github.com/mattermost/mattermost server dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

github.com/mattermost/mattermost-server fixed: 4.1.2 
Upgrade github.com/mattermost/mattermost-server to 4.1.2
github.com/mattermost/mattermost-server fixed: 4.2.1 
Upgrade github.com/mattermost/mattermost-server to 4.2.1
github.com/mattermost/mattermost-server fixed: 4.3.0 
Upgrade github.com/mattermost/mattermost-server to 4.3.0
Verify Direct and Transitive Dependencies

Run 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

How to Check if You Are Affected

To determine whether your application is affected by CVE-2017-18889, inspect your project dependencies for Github.com/mattermost/mattermost server:

inspect dependencies for github.com/mattermost/mattermost-server

Analyze the terminal output to locate any version of Github.com/mattermost/mattermost server in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.1.2), 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-20: Improper Input Validation, where the product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. In Github.com/mattermost/mattermost server, 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

An issue was discovered in Mattermost Server before 4.3.0, 4.2.1, and 4.1.2. An attacker could create fictive system-message posts via webhooks and slash commands, in the v3 or v4 REST API.

CVE-2017-18889 Affected Github.com/mattermost/mattermost server Versions

3 component(s)
Fixed Versions:
4.1.24.2.14.3.0
Product / Package Ecosystem Affected Versions Fixed Version
github.com/mattermost/mattermost-server
golang/github.com/mattermost/mattermost-server
Go
< 4.1.2
4.1.2
github.com/mattermost/mattermost-server
golang/github.com/mattermost/mattermost-server
Go
≥ 4.2.0-rc1
< 4.2.1
4.2.1
github.com/mattermost/mattermost-server
golang/github.com/mattermost/mattermost-server
Go
≥ 4.3.0-rc1
< 4.3.0
4.3.0

References

NVD — CVE-2017-18889 NVD
https://nvd.nist.gov/vuln/detail/CVE-2017-18889
Github.com/mattermost/mattermost server Source Repository REPOSITORY
https://github.com/mattermost/mattermost
Github.com/mattermost/mattermost server Security Information SECURITY
https://mattermost.com/security-updates

Frequently Asked Questions

What is CVE-2017-18889?
CVE-2017-18889 is a security vulnerability in Github.com/mattermost/mattermost server involving Mattermost Server is vulnerable to webhook and slash command manipulation under CWE-20: Improper Input Validation.
Which Github.com/mattermost/mattermost server versions are affected?
Affected versions include releases prior to 4.1.2, 4.2.1, 4.3.0 across affected packages: github.com/mattermost/mattermost-server.
What version fixes CVE-2017-18889?
Upgrading to 4.1.2, 4.2.1, 4.3.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/mattermost/mattermost-server affected?
Yes, github.com/mattermost/mattermost-server is affected in releases prior to 4.1.2, 4.2.1, 4.3.0. Upgrade your dependency to 4.1.2, 4.2.1, 4.3.0 or later.
What is the CVSS score of CVE-2017-18889?
CVE-2017-18889 has a CVSS v3.1 base score of 4.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.
What CWE is associated with CVE-2017-18889?
CVE-2017-18889 is classified under CWE-20: Improper Input Validation (The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.).
How can I check Go dependencies for CVE-2017-18889?
Run the dependency tree command: 'inspect dependencies for github.com/mattermost/mattermost-server'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-jp57-4x34-5v94",
  "modified" : "2025-12-05T22:00:33Z",
  "published" : "2022-05-24T17:21:04Z",
  "aliases" : [ "CVE-2017-18889" ],
  "summary" : "Mattermost Server is vulnerable to webhook and slash command manipulation",
  "details" : "An issue was discovered in Mattermost Server before 4.3.0, 4.2.1, and 4.1.2. An attacker could create fictive system-message posts via webhooks and slash commands, in the v3 or v4 REST API.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.1.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.2.0-rc1"
      }, {
        "fixed" : "4.2.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.3.0-rc1"
      }, {
        "fixed" : "4.3.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2017-18889"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/mattermost/mattermost"
  }, {
    "type" : "WEB",
    "url" : "https://mattermost.com/security-updates"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2025-12-05T22:00:33Z",
    "nvd_published_at" : "2020-06-19T19:15:00Z"
  }
}