CVE-2026-6339
Mattermost versions 11.5.x <= 11.5.1, 11.4.x <= 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint which allows an authenticated channel member to force the reveal of a burn-on-read message without recipient consent via a crafted Markdown image tag.. Mattermost Advisory ID: MMSA-2026-00636
- CVSS 3.1
- 4.3
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N - EPSS
- 0.1% chance of exploitation in the next 30 days; higher than 1% of CVEs (scores of 2026-10-25)
- CWE
- CWE-346
- Published
- Modified
- Record from
- the NVD, synced
Affected
- mattermost:mattermost_server
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-xvcx-mgpc-5xh3 | Go | github.com/mattermost/mattermost/server/v8 | >=11.5.0 <11.5.2 | 11.5.2 |
| GHSA-xvcx-mgpc-5xh3 | Go | github.com/mattermost/mattermost/server/v8 | >=11.4.0 <11.4.4 | 11.4.4 |
| GHSA-xvcx-mgpc-5xh3 | Go | github.com/mattermost/mattermost/server/v8 | <8.0.0-20260327001745-7a339a6438f5 | 8.0.0-20260327001745-7a339a6438f5 |
| GHSA-xvcx-mgpc-5xh3 | Go | github.com/mattermost/mattermost-server | <5.3.2-0.20260327001745-7a339a6438f5 | 5.3.2-0.20260327001745-7a339a6438f5 |
| GO-2026-5769 | Go | github.com/mattermost/mattermost-server | >=11.4.0+incompatible <11.4.4+incompatible >=11.5.0+incompatible <11.5.2+incompatible | 11.4.4+incompatible, 11.5.2+incompatible |
| GO-2026-5769 | Go | github.com/mattermost/mattermost-server/v5 | all versions | no fix published |
| GO-2026-5769 | Go | github.com/mattermost/mattermost-server/v6 | all versions | no fix published |
| GO-2026-5769 | Go | github.com/mattermost/mattermost/server/v8 | <8.0.0-20260327001745-7a339a6438f5 | 8.0.0-20260327001745-7a339a6438f5 |