| Package | Affected versions | Patched versions |
|---|---|---|
| github.com/mattermost/mattermost-server | ≥ 10.11.0-rc1, < 10.11.11≥ 10.11.0-rc1+incompatible, < 10.11.11+incompatible≥ 11.2.0-rc1, < 11.2.3≥ 11.2.0-rc1+incompatible, < 11.2.3+incompatible≥ 11.3.0-rc1, < 11.3.1≥ 11.3.0-rc1+incompatible, < 11.3.1+incompatible< 5.3.2-0.20260129181235-1346cf529aef | 10.11.1110.11.11+incompatible11.2.311.2.3+incompatible11.3.111.3.1+incompatible5.3.2-0.20260129181235-1346cf529aef |
| github.com/mattermost/mattermost-server/v5 | all versions | |
| github.com/mattermost/mattermost-server/v6 | all versions | |
| github.com/mattermost/mattermost/server/v8 | < 8.0.0-20260129181235-1346cf529aef | 8.0.0-20260129181235-1346cf529aef |
| mattermost server | ≥ 10.11.0, < 10.11.11≥ 11.2.0, < 11.2.3≥ 11.3.0, < 11.3.1 | 10.11.1111.2.311.3.1 |
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly validate User-Agent header tokens which allows an authenticated attacker to cause a request panic via a specially crafted User-Agent header. Mattermost Advisory ID: MMSA-2026-00586
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