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TI-2025-20657 Aliases CVE-2025-27936GHSA-2j87-p623-8cc2

Webhook Secret Exposure via Timing attack in MSteams plugin

Priority LOW 26CWE-208Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Impact type
Information disclosure
Confidentiality · integrity · availability
High · None · None
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub. Impact type from CWE-208.

Summary

Mattermost Plugin MSTeams versions <2.1.0 and Mattermost Server versions 10.5.x <=10.5.1 with the MS Teams plugin enabled fail to perform constant time comparison on a MSTeams plugin webhook secret which allows an attacker to retrieve the webhook secret of the MSTeams plugin via a timing attack during webhook secret comparison.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00345 28th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 10.6.0, 10.5.2github.com/mattermost/mattermost/server/v8 (Go): 10.5.2, 8.0.0-20250314142426-c049748b8863+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
MattermostMattermost10.5.0 – 10.5.110.6.0, 10.5.2Patch availableCNA
—github.com/mattermost/mattermost/server/v8 (Go)10.5.0 to before 10.5.210.5.2Patch availableGHSA-2j87-p623-8cc2
—github.com/mattermost/mattermost/server/v8 (Go)before 8.0.0-20250314142426-c049748b88638.0.0-20250314142426-c049748b8863Patch availableGHSA-2j87-p623-8cc2
—github.com/mattermost/mattermost-plugin-msteams (Go)before 2.1.02.1.0Patch availableGHSA-2j87-p623-8cc2
  • Mattermost VendorMattermost Affected 10.5.0 – 10.5.1 Fixed in 10.6.0, 10.5.2 Patch available CNA
  • github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 10.5.0 to before 10.5.2 Fixed in 10.5.2 Patch available GHSA-2j87-p623-8cc2
  • github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected before 8.0.0-20250314142426-c049748b8863 Fixed in 8.0.0-20250314142426-c049748b8863 Patch available GHSA-2j87-p623-8cc2
  • github.com/mattermost/mattermost-plugin-msteams (Go) Vendor— Affected before 2.1.0 Fixed in 2.1.0 Patch available GHSA-2j87-p623-8cc2

CPE configurations NVD · 2

CPEVersionsRoleVendor
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*before 10.5.2VulnerableMattermost
cpe:2.3:a:mattermost:ms_teams:*:*:*:*:*:*:*:*before 2.1.0VulnerableMattermost
  • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions before 10.5.2 Vulnerable ·Mattermost
  • cpe:2.3:a:mattermost:ms_teams:*:*:*:*:*:*:*:* Versions before 2.1.0 Vulnerable ·Mattermost

Remediation

  • Fix · CNA Mattermost (Mattermost) Fixed in 10.6.0, 10.5.2
  • Fix · GHSA-2j87-p623-8cc2 github.com/mattermost/mattermost/server/v8 (Go) Fixed in 10.5.2 Advisory →
  • Fix · GHSA-2j87-p623-8cc2 github.com/mattermost/mattermost/server/v8 (Go) Fixed in 8.0.0-20250314142426-c049748b8863 Advisory →
  • Fix · GHSA-2j87-p623-8cc2 github.com/mattermost/mattermost-plugin-msteams (Go) Fixed in 2.1.0 Advisory →

Timeline

  1. 2026-10-02 Threatist record created from CVE-2025-27936
  2. 2026-10-03 Alias added: GHSA-2j87-p623-8cc2

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