CVE-2026-96259

Description

Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network addresses and read the responses via the configured OAuth token and userinfo endpoints.. Mattermost Advisory ID: MMSA-2026-00776

Overview

State: PUBLISHED
Assigner (CNA): Mattermost
CVSS severity: MEDIUM
CVSS score: 5.5 / 10
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N
Effective score: 5.5 / 10 MEDIUM source: CNA overview
CWE(s): CWE-918
Reserved: 2026-09-22
Published: 2026-09-22 20:34 UTC
Last updated: 2026-09-22 20:34 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/96xxx/CVE-2026-96259.json

NVD triage scoring NVD CVE 2.0

Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.

NVD published: 2026-09-22 21:17:34 UTC
NVD last modified: 2026-09-22 21:17:34 UTC
NVD CVSS v3.1: 5.5 / 10 MEDIUM source: responsibledisclosure@mattermost.com
NVD CVSS vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N
Exploitability subscore: 2.3 / 10
Impact subscore: 2.7 / 10

European Union Vulnerability Database ENISA EUVD

ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.

EUVD ID: EUVD-2026-84869
Assigner: Mattermost
Published: Sep 22, 2026, 8:34:20 PM
Updated: Sep 22, 2026, 8:34:20 PM
EUVD base score (CVSS 3.1): 5.5 / 10
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N
EUVD-reported EPSS: 0.0000
Vendors: Mattermost
Products: Mattermost (11.7.0 ≤11.7.10)

Mattermost (11.9.0 ≤11.9.1)

Mattermost (11.8.0 ≤11.8.5)

Mattermost (11.10.0 ≤11.10.1)
Aliases: GHSA-j85c-qqpv-57m3

ENISA description: Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network addresses and read the responses via the configured OAuth token and userinfo endpoints.. Mattermost Advisory ID: MMSA-2026-00776

EUVD references (1)

https://mattermost.com/security-updates

Affected products (1)

Vendor	Product	Versions	Platforms
Mattermost	Mattermost	`11.9.0` (affected), `11.8.0` (affected), `11.7.0` (affected), `11.10.0` (affected), `11.11.0` (unaffected), `11.9.2` (unaffected), `11.8.6` (unaffected), `11.7.11` (unaffected), `11.10.2` (unaffected)	—

Vendor references (1)

References embedded in the original CVE record by the assigning CNA.

MMSA-2026-00776 vendor-advisory

Web references (0)

DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.

No web references attached yet.

NVD-tagged references (1)

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

https://mattermost.com/security-updates responsibledisclosure@mattermost.com

Remediations (10)

CISA Warns Actively Exploited Microsoft SharePoint RCE Flaw Requires ...

web:cyberpress.org

The Cybersecurity and Infrastructure Security Agency (CISA) has added a critical Microsoft SharePoint Server vulnerability to its Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild and setting an aggressive remediation deadline for federal agencies and organizations running the platform.

2026-09-23 15:39 UTC
Security Update Guide - Microsoft

web:msrc.microsoft.com

The Microsoft Security Response Center (MSRC) investigates all reports of security vulnerabilities affecting Microsoft products and services, and provides the information here as part of the ongoing effort to help you manage security risks and help keep your systems protected.

2026-09-23 15:39 UTC
Cisco Advance Notification for Publication of September 16, 2026 ...

web:sec.cloudapps.cisco.com

On September 16, 2026 , the Cisco Product Security Incident Response Team (PSIRT) published the advisories that are listed in the following tables. To remediate these vulnerabilities, Cisco strongly recommends that customers upgrade to the fixed software that is indicated in the advisories. For more information about changes in Cisco PSIRT vulnerability disclosure, see Strengthening the ...

2026-09-23 15:39 UTC
Microsoft Patch Tracker (September 2026): Exploit-Ranked | Senserva

web:senserva.com

Every Microsoft security patch (KB) and the CVEs it fixes, with severity, CVSS, and CISA KEV status. Cross-linked to the CVE reference.

2026-09-23 15:39 UTC
SAP Security Patch Day - June 2026

web:support.sap.com

SAP security Patch Day Bulletin This post shares the information on security notes that remediate vulnerabilities discovered in SAP products. SAP strongly recommends that the customer visits the support portal and applies patches on priority to protect their SAP landscape. On 9th of June 2026 , SAP security patch day saw the release of 15 new security notes.

2026-09-23 15:39 UTC
SAP Security Patch Day - September 2026

web:support.sap.com

SAP Security Patch Day Bulletin This post shares the information on security notes that remediate vulnerabilities discovered in SAP products. SAP strongly recommends that the customer visits the support portal and applies patches on priority to protect their SAP landscape. On 8 th of September 2026 , SAP security patch day saw the release of 19 new security notes. There is 1 update to ...

2026-09-23 15:39 UTC
SharePoint Vulnerability CVE-2026-45659 Exploited [2026]

web:tech-insider.org

SharePoint vulnerability CVE - 2026 -45659 is under active exploitation. See the CVSS 8.8 RCE risk, affected on-prem versions and CISA's July 4 patch deadline.

2026-09-23 15:39 UTC
Microsoft Patches SharePoint RCE Flaw CVE-2026-45659 ... - The Hacker News

web:thehackernews.com

Microsoft released fixes for SharePoint remote code execution vulnerability CVE - 2026 -45659 with a CVSS score of 8.8.

2026-09-23 15:39 UTC
CVE-2026-45659: Microsoft SharePoint Server RCE Vulnerability

web:www.sentinelone.com

CVE - 2026 -45659 is a remote code execution vulnerability in Microsoft SharePoint Server. Learn about its impact, affected versions, and mitigation methods.

2026-09-23 15:39 UTC
SharePoint CVEs FAQ: CVE-2026-56164, CVE-2026-32201, CVE-2026 ... - Tenable

web:www.tenable.com

CISA confirmed exploitation of three SharePoint Server CVEs . Patches, AMSI IoCs, and details on CVE - 2026 -32201, CVE - 2026 -45659, CVE - 2026 -56164.

2026-09-23 15:39 UTC

AI Forensic Analysis

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Raw JSON

The full cvelistV5 record. Download as CVE-2026-96259.json.

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Mattermost",
          "vendor": "Mattermost",
          "versions": [
            {
              "lessThanOrEqual": "11.9.1",
              "status": "affected",
              "version": "11.9.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "11.8.5",
              "status": "affected",
              "version": "11.8.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "11.7.10",
              "status": "affected",
              "version": "11.7.0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "11.10.1",
              "status": "affected",
              "version": "11.10.0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "11.11.0"
            },
            {
              "status": "unaffected",
              "version": "11.9.2"
            },
            {
              "status": "unaffected",
              "version": "11.8.6"
            },
            {
              "status": "unaffected",
              "version": "11.7.11"
            },
            {
              "status": "unaffected",
              "version": "11.10.2"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "n1nj4sec"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network addresses and read the responses via the configured OAuth token and userinfo endpoints.. Mattermost Advisory ID: MMSA-2026-00776"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "privilegesRequired": "HIGH",
            "scope": "CHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-918",
              "description": "CWE-918: Server-Side Request Forgery (SSRF)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-22T20:34:20.872Z",
        "orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee",
        "shortName": "Mattermost"
      },
      "references": [
        {
          "name": "MMSA-2026-00776",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://mattermost.com/security-updates"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "Update Mattermost to versions 11.11.0, 11.9.2, 11.8.6, 11.7.11, 11.10.2 or higher."
        }
      ],
      "source": {
        "advisory": "MMSA-2026-00776",
        "defect": [
          "https://mattermost.atlassian.net/browse/MM-70502"
        ],
        "discovery": "EXTERNAL"
      },
      "title": "Mattermost server-side request forgery via OAuth endpoints configurable by a System Administrator",
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee",
    "assignerShortName": "Mattermost",
    "cveId": "CVE-2026-96259",
    "datePublished": "2026-09-22T20:34:20.872Z",
    "dateReserved": "2026-09-22T19:59:57.887Z",
    "dateUpdated": "2026-09-22T20:34:20.872Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}