CVE-2026-24458: Github.com/mattermost/mattermost/server/v8 Mattermost Fails To Properly Handle Vulnerability

HIGH
Advisory Identifier: GHSA-m5rv-56xx-hfc6
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CVSS 7.5
CWE-770
Published
Advisory Summary

CVE-2026-24458 is a HIGH (CVSS 7.5) mattermost fails to properly handle vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) affecting Github.com/mattermost/mattermost/server/v8 libraries in the Go ecosystem. The issue involves mattermost fails to properly handle very long passwords. Remediation is available by upgrading affected packages to version 8.0.0-20260129164748-7201f42d955f, 5.3.2-0.20260129164748-7201f42d955f, 10.11.11, 11.2.3, 11.3.1.

CVE-2026-24458 at a Glance

CVE Identifier CVE-2026-24458
GHSA Identifier GHSA-m5rv-56xx-hfc6
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-770: Allocation of Resources Without Limits or Throttling
Affected Product Github.com/mattermost/mattermost/server/v8
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

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

How to Fix CVE-2026-24458

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.

github.com/mattermost/mattermost/server/v8 fixed: 8.0.0-20260129164748-7201f42d955f 
Upgrade github.com/mattermost/mattermost/server/v8 to 8.0.0-20260129164748-7201f42d955f
github.com/mattermost/mattermost-server fixed: 5.3.2-0.20260129164748-7201f42d955f 
Upgrade github.com/mattermost/mattermost-server to 5.3.2-0.20260129164748-7201f42d955f
github.com/mattermost/mattermost-server fixed: 10.11.11 
Upgrade github.com/mattermost/mattermost-server to 10.11.11
github.com/mattermost/mattermost-server fixed: 11.2.3 
Upgrade github.com/mattermost/mattermost-server to 11.2.3
github.com/mattermost/mattermost-server fixed: 11.3.1 
Upgrade github.com/mattermost/mattermost-server to 11.3.1
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/v8

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-24458, inspect your project dependencies for Github.com/mattermost/mattermost/server/v8:

inspect dependencies for github.com/mattermost/mattermost/server/v8

Analyze 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 8.0.0-20260129164748-7201f42d955f), 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/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

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly handle very long passwords, which allows an attacker to overload the server CPU and memory via executing login attempts with multi-megabyte passwords. Mattermost Advisory ID: MMSA-2026-00587

CVE-2026-24458 Affected Github.com/mattermost/mattermost/server/v8 Versions

5 component(s)
Fixed Versions:
8.0.0-20260129164748-7201f42d955f5.3.2-0.20260129164748-7201f42d955f10.11.1111.2.311.3.1
Product / Package Ecosystem Affected Versions Fixed Version
github.com/mattermost/mattermost/server/v8
golang/github.com/mattermost/mattermost/server/v8
Go
< 8.0.0-20260129164748-7201f42d955f
8.0.0-20260129164748-7201f42d955f
github.com/mattermost/mattermost-server
golang/github.com/mattermost/mattermost-server
Go
< 5.3.2-0.20260129164748-7201f42d955f
5.3.2-0.20260129164748-7201f42d955f
github.com/mattermost/mattermost-server
golang/github.com/mattermost/mattermost-server
Go
≥ 10.11.0-rc1
< 10.11.11
10.11.11
github.com/mattermost/mattermost-server
golang/github.com/mattermost/mattermost-server
Go
≥ 11.2.0-rc1
< 11.2.3
11.2.3
github.com/mattermost/mattermost-server
golang/github.com/mattermost/mattermost-server
Go
≥ 11.3.0-rc1
< 11.3.1
11.3.1

References

NVD — CVE-2026-24458 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-24458
Security Fix Commit FIX COMMIT
https://github.com/mattermost/mattermost/commit/7201f42d955f1bc44719b862132546626b60a180
Github.com/mattermost/mattermost/server/v8 Source Repository REPOSITORY
https://github.com/mattermost/mattermost
Github.com/mattermost/mattermost/server/v8 Security Information SECURITY
https://mattermost.com/security-updates

Frequently Asked Questions

What is CVE-2026-24458?
CVE-2026-24458 is a security vulnerability in Github.com/mattermost/mattermost/server/v8 involving Mattermost fails to properly handle very long passwords under CWE-770: Allocation of Resources Without Limits or Throttling.
Which Github.com/mattermost/mattermost/server/v8 versions are affected?
Affected versions include releases prior to 8.0.0-20260129164748-7201f42d955f, 5.3.2-0.20260129164748-7201f42d955f, 10.11.11, 11.2.3, 11.3.1 across affected packages: github.com/mattermost/mattermost/server/v8, github.com/mattermost/mattermost-server.
What version fixes CVE-2026-24458?
Upgrading to 8.0.0-20260129164748-7201f42d955f, 5.3.2-0.20260129164748-7201f42d955f, 10.11.11, 11.2.3, 11.3.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/mattermost/mattermost/server/v8 affected?
Yes, github.com/mattermost/mattermost/server/v8 is affected in releases prior to 8.0.0-20260129164748-7201f42d955f. Upgrade your dependency to 8.0.0-20260129164748-7201f42d955f or later.
Is github.com/mattermost/mattermost-server affected?
Yes, github.com/mattermost/mattermost-server is affected in releases prior to 5.3.2-0.20260129164748-7201f42d955f, 10.11.11, 11.2.3, 11.3.1. Upgrade your dependency to 5.3.2-0.20260129164748-7201f42d955f, 10.11.11, 11.2.3, 11.3.1 or later.
What is the CVSS score of CVE-2026-24458?
CVE-2026-24458 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-24458?
CVE-2026-24458 is classified under CWE-770: Allocation of Resources Without Limits or Throttling (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.).
How can I check Go dependencies for CVE-2026-24458?
Run the dependency tree command: 'inspect dependencies for github.com/mattermost/mattermost/server/v8'. 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-m5rv-56xx-hfc6",
  "modified" : "2026-03-17T19:59:16Z",
  "published" : "2026-03-16T15:30:42Z",
  "aliases" : [ "CVE-2026-24458" ],
  "summary" : "Mattermost fails to properly handle very long passwords",
  "details" : "Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly handle very long passwords, which allows an attacker to overload the server CPU and memory via executing login attempts with multi-megabyte passwords. Mattermost Advisory ID: MMSA-2026-00587",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
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      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost/server/v8"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "8.0.0-20260129164748-7201f42d955f"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.3.2-0.20260129164748-7201f42d955f"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "10.11.0-rc1"
      }, {
        "fixed" : "10.11.11"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "11.2.0-rc1"
      }, {
        "fixed" : "11.2.3"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "11.3.0-rc1"
      }, {
        "fixed" : "11.3.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-24458"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/commit/7201f42d955f1bc44719b862132546626b60a180"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/mattermost/mattermost"
  }, {
    "type" : "WEB",
    "url" : "https://mattermost.com/security-updates"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-17T19:59:16Z",
    "nvd_published_at" : "2026-03-16T14:18:16Z"
  }
}