Quick answers
- Is CVE-2026-93849 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-93849 being exploited in the wild.
- How severe is CVE-2026-93849?
- Medium severity, with a CVSS score of 6.5, published 26 October 2026.
- Which products and versions are affected?
- Mattermost Server 11.7.x up to 11.7.10, 11.8.x up to 11.8.5, 11.9.x up to 11.9.1, 11.10.x up to 11.10.1.
- Is there a fix for CVE-2026-93849?
- Yes: fixed in Mattermost Server 11.7.11, 11.8.6, 11.9.2, 11.10.2 (or later versions in each branch). Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-93849 attacked?
- It is attacked over the network, in a hosted service.
- Am I affected by CVE-2026-93849?
- Check whether you run Mattermost Server at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: Mattermost Server 11.7.11, 11.8.6, 11.9.2, 11.10.2 (or later versions in each branch)
Technical details
The WebSocket msgpack decoder in Mattermost lacks allocation limits on the byte-string decode path, allowing an authenticated attacker to declare a Bin32 payload with lengths up to 4,294,967,295 bytes via a crafted binary frame. This triggers excessive server memory allocation resulting in denial of service. Authentication is required; the vulnerability is exploited over the network via the WebSocket protocol.
Affected products
- Mattermost Mattermost Server 11.7.x up to 11.7.10, 11.8.x up to 11.8.5, 11.9.x up to 11.9.1, 11.10.x up to 11.10.1
Timeline
- 2026-10-26: disclosed