Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Mattermost Server (github.com/mattermost/mattermost/server/v8) versions 10.5.0 and 10.5.1 and the Mattermost MS Teams plugin (github.com/mattermost/mattermost-plugin-msteams) versions before 2.1.0 are affected. When the MS Teams plugin is enabled, the webhook secret comparison is not constant time, so an attacker who can send requests to the webhook may recover the secret through a timing attack. Upgrade Mattermost Server to 10.5.2 or a fixed 8.x build, and upgrade the MS Teams plugin to 2.1.0.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 5.3 | Medium | 3.1 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N | CNA (Mattermost) |
- CISA KEV Not listed.
- EPSS 0.0034, the 28th percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:14 UTC First seen by agentprime
- 31 Oct 2026, 14:14 UTC Confirmed by OSV