CVE-2026-25780: Github.com/mattermost/mattermost/server/v8 Mattermost Fails To Bound Memory Vulnerability

MODERATE
Advisory Identifier: GHSA-xv2p-wchj-qjhp
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CVSS 4.3
CWE-789
Published
Advisory Summary

CVE-2026-25780 is a MODERATE (CVSS 4.3) mattermost fails to bound memory vulnerability (CWE-789: Memory Allocation with Excessive Size Value) affecting Github.com/mattermost/mattermost/server/v8 libraries in the Go ecosystem. The issue involves mattermost fails to bound memory allocation when processing doc files. Remediation is available by upgrading affected packages to version 8.0.0-20260123215601-86797c508c44, 5.3.2-0.20260123215601-86797c508c44, 10.11.11, 11.2.3, 11.3.1.

CVE-2026-25780 at a Glance

CVE Identifier CVE-2026-25780
GHSA Identifier GHSA-xv2p-wchj-qjhp
Severity MODERATE
CVSS v3.1 Base Score 4.3
CWE Classification CWE-789: Memory Allocation with Excessive Size Value
Affected Product Github.com/mattermost/mattermost/server/v8
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:N/A:L).

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 None (I:N)
Availability Low (A:L)

How to Fix CVE-2026-25780

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: 8.0.0-20260123215601-86797c508c44 
Upgrade github.com/mattermost/mattermost/server/v8 to 8.0.0-20260123215601-86797c508c44
github.com/mattermost/mattermost-server fixed: 5.3.2-0.20260123215601-86797c508c44 
Upgrade github.com/mattermost/mattermost-server to 5.3.2-0.20260123215601-86797c508c44
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-2026-25780, 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 8.0.0-20260123215601-86797c508c44), 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-789: Memory Allocation with Excessive Size Value, where the product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to 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 bound memory allocation when processing DOC files which allows an authenticated attacker to cause server memory exhaustion and denial of service via uploading a specially crafted DOC file.. Mattermost Advisory ID: MMSA-2026-00581

CVE-2026-25780 Affected Github.com/mattermost/mattermost/server/v8 Versions

5 component(s)
Fixed Versions:
8.0.0-20260123215601-86797c508c445.3.2-0.20260123215601-86797c508c4410.11.1111.2.311.3.1
Product / Package Ecosystem Affected Versions Fixed Version
github.com/mattermost/mattermost/server/v8
golang/github.com/mattermost/mattermost/server/v8
Go
< 8.0.0-20260123215601-86797c508c44
8.0.0-20260123215601-86797c508c44
github.com/mattermost/mattermost-server
golang/github.com/mattermost/mattermost-server
Go
< 5.3.2-0.20260123215601-86797c508c44
5.3.2-0.20260123215601-86797c508c44
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-2026-25780 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-25780
Security Fix Commit FIX COMMIT
https://github.com/mattermost/mattermost/commit/86797c508c444e299b20889ce241fde505a402cc
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-2026-25780?
CVE-2026-25780 is a security vulnerability in Github.com/mattermost/mattermost/server/v8 involving Mattermost fails to bound memory allocation when processing DOC files under CWE-789: Memory Allocation with Excessive Size Value.
Which Github.com/mattermost/mattermost/server/v8 versions are affected?
Affected versions include releases prior to 8.0.0-20260123215601-86797c508c44, 5.3.2-0.20260123215601-86797c508c44, 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-2026-25780?
Upgrading to 8.0.0-20260123215601-86797c508c44, 5.3.2-0.20260123215601-86797c508c44, 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 8.0.0-20260123215601-86797c508c44. Upgrade your dependency to 8.0.0-20260123215601-86797c508c44 or later.
Is github.com/mattermost/mattermost-server affected?
Yes, github.com/mattermost/mattermost-server is affected in releases prior to 5.3.2-0.20260123215601-86797c508c44, 10.11.11, 11.2.3, 11.3.1. Upgrade your dependency to 5.3.2-0.20260123215601-86797c508c44, 10.11.11, 11.2.3, 11.3.1 or later.
What is the CVSS score of CVE-2026-25780?
CVE-2026-25780 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:N/A:L.
What CWE is associated with CVE-2026-25780?
CVE-2026-25780 is classified under CWE-789: Memory Allocation with Excessive Size Value (The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.).
How can I check Go dependencies for CVE-2026-25780?
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-xv2p-wchj-qjhp",
  "modified" : "2026-03-17T19:59:29Z",
  "published" : "2026-03-16T15:30:42Z",
  "aliases" : [ "CVE-2026-25780" ],
  "summary" : "Mattermost fails to bound memory allocation when processing DOC files",
  "details" : "Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to bound memory allocation when processing DOC files which allows an authenticated attacker to cause server memory exhaustion and denial of service via uploading a specially crafted DOC file.. Mattermost Advisory ID: MMSA-2026-00581",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost/server/v8"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "8.0.0-20260123215601-86797c508c44"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/mattermost/mattermost-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
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      }, {
        "fixed" : "5.3.2-0.20260123215601-86797c508c44"
      } ]
    } ]
  }, {
    "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-2026-25780"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/mattermost/commit/86797c508c444e299b20889ce241fde505a402cc"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/mattermost/mattermost"
  }, {
    "type" : "WEB",
    "url" : "https://mattermost.com/security-updates"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-789" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-17T19:59:29Z",
    "nvd_published_at" : "2026-03-16T14:18:23Z"
  }
}