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TI-2026-00753 Aliases CVE-2026-0999GHSA-3c9r-7f29-qp32

Authentication bypass via userID login when email and username login are disabled

Priority LOW 24CWE-303Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
Low · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub.

Summary

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to properly validate login method restrictions which allows an authenticated user to bypass SSO-only login requirements via userID-based authentication. Mattermost Advisory ID: MMSA-2025-00548

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.002 9th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 11.3.0, 11.1.3, 10.11.10 +1github.com/mattermost/mattermost/server/v8 (Go): 8.0.0-20251212052346-61651b0df7ea+1 more product

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MattermostMattermost11.1.0 – 11.1.2; 10.11.0 – 10.11.9; 11.2.0 – 11.2.111.3.0, 11.1.3, 10.11.10, 11.2.2Patch availableCNA
—github.com/mattermost/mattermost/server/v8 (Go)before 8.0.0-20251212052346-61651b0df7ea8.0.0-20251212052346-61651b0df7eaPatch availableGHSA-3c9r-7f29-qp32
—github.com/mattermost/mattermost-server (Go)11.1.0 and later—No fix listedGHSA-3c9r-7f29-qp32
—github.com/mattermost/mattermost-server (Go)10.11.0 and later—No fix listedGHSA-3c9r-7f29-qp32
—github.com/mattermost/mattermost-server (Go)11.2.0 and later—No fix listedGHSA-3c9r-7f29-qp32
—github.com/mattermost/mattermost-server (Go)before 5.3.2-0.20251212052346-61651b0df7ea5.3.2-0.20251212052346-61651b0df7eaPatch availableGHSA-3c9r-7f29-qp32
  • Mattermost VendorMattermost Affected 11.1.0 – 11.1.2; 10.11.0 – 10.11.9; 11.2.0 – 11.2.1 Fixed in 11.3.0, 11.1.3, 10.11.10, 11.2.2 Patch available CNA
  • github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected before 8.0.0-20251212052346-61651b0df7ea Fixed in 8.0.0-20251212052346-61651b0df7ea Patch available GHSA-3c9r-7f29-qp32
  • github.com/mattermost/mattermost-server (Go) Vendor— Affected 11.1.0 and later Fixed in — No fix listed GHSA-3c9r-7f29-qp32
  • github.com/mattermost/mattermost-server (Go) Vendor— Affected 10.11.0 and later Fixed in — No fix listed GHSA-3c9r-7f29-qp32
  • github.com/mattermost/mattermost-server (Go) Vendor— Affected 11.2.0 and later Fixed in — No fix listed GHSA-3c9r-7f29-qp32
  • github.com/mattermost/mattermost-server (Go) Vendor— Affected before 5.3.2-0.20251212052346-61651b0df7ea Fixed in 5.3.2-0.20251212052346-61651b0df7ea Patch available GHSA-3c9r-7f29-qp32

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*10.11.0 to before 10.11.10; 11.1.0 to before 11.1.3; 11.2.0 to before 11.2.2VulnerableMattermost
  • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 10.11.0 to before 10.11.10; 11.1.0 to before 11.1.3; 11.2.0 to before 11.2.2 Vulnerable ·Mattermost

Remediation

  • Fix · CNA Mattermost (Mattermost) Fixed in 11.3.0, 11.1.3, 10.11.10, 11.2.2
  • Fix · GHSA-3c9r-7f29-qp32 github.com/mattermost/mattermost/server/v8 (Go) Fixed in 8.0.0-20251212052346-61651b0df7ea Advisory →
  • Fix · GHSA-3c9r-7f29-qp32 github.com/mattermost/mattermost-server (Go) Fixed in 5.3.2-0.20251212052346-61651b0df7ea Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-0999
  2. 2026-10-03 Alias added: GHSA-3c9r-7f29-qp32

References

Advisory 2

Other 2

  • TI-2025-18933 Arbitrary file read in Mattermost Boards via import & export board archive CVSS 3.1CRITICAL 9.9
  • TI-2025-04465 Path Traversal Leading to RCE by Any Authenticated Mattermost User CVSS 3.1CRITICAL 9.9
  • TI-2017-14068 An issue was discovered in Mattermost Server before 3.6.2. CVSS 3.1CRITICAL 9.8
  • TI-2017-14060 An issue was discovered in Mattermost Server before 3.8.2, 3.7.5, and 3.6.7. CVSS 3.1CRITICAL 9.8
  • TI-2017-14048 An issue was discovered in Mattermost Server before 4.1.0, 4.0.4, and 3.10.3. CVSS 3.1CRITICAL 9.8
  • TI-2025-14360 Arbitrary file read via block duplication in Mattermost Boards CVSS 3.1CRITICAL 9.9
See all 505 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences