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TI-2026-17290 Aliases CVE-2026-21388GHSA-x274-8qfc-hrgf

Unbounded Request Body Read in MS Teams Plugin {{/lifecycle}} Webhook Endpoint

Priority LOW 29CWE-770Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub. Impact type from CWE-770.

Summary

Mattermost Plugins versions <=2.3.1 fail to limit the request body size on the {{/lifecycle}} webhook endpoint which allows an authenticated attacker to cause memory exhaustion and denial of service via sending an oversized JSON payload. Mattermost Advisory ID: MMSA-2026-00610

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00317 24th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 2.3.2.0github.com/mattermost/mattermost-plugin-msteams (Go): 1.15.1-0.20260213190728-6fe4d295592e

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
MattermostMattermostup to 2.3.12.3.2.0Patch availableCNA
—github.com/mattermost/mattermost-plugin-msteams (Go)before 1.15.1-0.20260213190728-6fe4d295592e1.15.1-0.20260213190728-6fe4d295592ePatch availableGHSA-x274-8qfc-hrgf
  • Mattermost VendorMattermost Affected up to 2.3.1 Fixed in 2.3.2.0 Patch available CNA
  • github.com/mattermost/mattermost-plugin-msteams (Go) Vendor— Affected before 1.15.1-0.20260213190728-6fe4d295592e Fixed in 1.15.1-0.20260213190728-6fe4d295592e Patch available GHSA-x274-8qfc-hrgf

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*up to 2.3.1VulnerableMattermost
  • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions up to 2.3.1 Vulnerable ·Mattermost

Remediation

  • Fix · CNA Mattermost (Mattermost) Fixed in 2.3.2.0
  • Fix · GHSA-x274-8qfc-hrgf github.com/mattermost/mattermost-plugin-msteams (Go) Fixed in 1.15.1-0.20260213190728-6fe4d295592e Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-21388
  2. 2026-10-03 Alias added: GHSA-x274-8qfc-hrgf

References

Advisory 2

Other 3

  • 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