CVE-2017-18886: Github.com/mattermost/mattermost server Mattermost Server Does Not Properly Vulnerability

HIGH
Advisory Identifier: GHSA-wvjg-33p9-938h
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CVSS 8.8
CWE-732
Published
Advisory Summary

CVE-2017-18886 is a HIGH (CVSS 8.8) mattermost server does not properly vulnerability (CWE-732: Incorrect Permission Assignment for Critical Resource) affecting Github.com/mattermost/mattermost server libraries in the Go ecosystem. The issue involves mattermost server does not properly restrict use of slash commands. Remediation is available by upgrading affected packages to version 4.1.2, 4.2.1, 4.3.0.

CVE-2017-18886 at a Glance

CVE Identifier CVE-2017-18886
GHSA Identifier GHSA-wvjg-33p9-938h
Severity HIGH
CVSS v3.1 Base Score 8.8
CWE Classification CWE-732: Incorrect Permission Assignment for Critical Resource
Affected Product Github.com/mattermost/mattermost server
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 8.8

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:H/I:H/A:H).

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 High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2017-18886

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-2017-18886, 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-732: Incorrect Permission Assignment for Critical Resource, where the product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors. 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. It allows a bypass of restrictions on use of slash commands.

CVE-2017-18886 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-2017-18886 NVD
https://nvd.nist.gov/vuln/detail/CVE-2017-18886
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-2017-18886?
CVE-2017-18886 is a security vulnerability in Github.com/mattermost/mattermost server involving Mattermost Server does not properly restrict use of slash commands under CWE-732: Incorrect Permission Assignment for Critical Resource.
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-2017-18886?
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-2017-18886?
CVE-2017-18886 has a CVSS v3.1 base score of 8.8 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2017-18886?
CVE-2017-18886 is classified under CWE-732: Incorrect Permission Assignment for Critical Resource (The product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors.).
How can I check Go dependencies for CVE-2017-18886?
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-wvjg-33p9-938h",
  "modified" : "2025-12-05T21:48:05Z",
  "published" : "2022-05-24T17:21:04Z",
  "aliases" : [ "CVE-2017-18886" ],
  "summary" : "Mattermost Server does not properly restrict use of slash commands",
  "details" : "An issue was discovered in Mattermost Server before 4.3.0, 4.2.1, and 4.1.2. It allows a bypass of restrictions on use of slash commands.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "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-2017-18886"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/mattermost/mattermost"
  }, {
    "type" : "WEB",
    "url" : "https://mattermost.com/security-updates"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-732" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2025-12-05T21:48:05Z",
    "nvd_published_at" : "2020-06-19T19:15:00Z"
  }
}