Answer in brief
CVE-2026-6046 records a Medium severity (CVSS 5.3) vulnerability in Mattermost doesn't validate that a username returned during bot registration belongs to a bot account. The current sources do not mark it as known exploited. The current feed maps github.com/mattermost/mattermost-server (go), github.com/mattermost/mattermost-server (go), github.com/mattermost/mattermost-server (go), github.com/mattermost/mattermost-server (go) and additional mapped packages. Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps github.com/mattermost/mattermost-server (go), github.com/mattermost/mattermost-server (go), github.com/mattermost/mattermost-server (go), github.com/mattermost/mattermost-server (go) and additional mapped packages. Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| github.com/mattermost/mattermost-servergo | =11.6.0 | 11.6.1 |
| github.com/mattermost/mattermost-servergo | >=11.5.0,<=11.5.4 | 11.5.5 |
| github.com/mattermost/mattermost-servergo | >=10.11.0,<=10.11.15 | 10.11.17 |
| github.com/mattermost/mattermost-servergo | >=11.6.0 <11.6.1 | 11.6.1 |
| github.com/mattermost/mattermost-servergo | >=11.5.0 <11.5.5 | 11.5.5 |
| github.com/mattermost/mattermost-servergo | >=10.11.0 <10.11.17 | 10.11.17 |
| github.com/mattermost/mattermost/server/v8go | >=8.0.0-20250731163400-5b955468ea1e,<8.0.0-20260428151657-c79c3831061a | 8.0.0-20260428151657-c79c3831061a |
| github.com/mattermost/mattermost/server/v8go | >=8.0.0-20250731163400-5b955468ea1e <8.0.0-20260428151657-c79c3831061a | 8.0.0-20260428151657-c79c3831061a |
Published upstream
Jun 12, 2026
Evidence: source:ghsa:source_dates:source-dates:recordSource modified
Aug 24, 2026
Evidence: source:ghsa:source_dates:source-dates:recordFirst seen by HOL
Aug 25, 2026
Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username. Mattermost Advisory ID: MMSA-2026-00649
Quoted source text, attributed separately from HOL analysis.