# CVE-2026-93849: Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 Mattermost fail to apply allocation limits to


- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 26 Oct 2026
- **Updated:** 26 Oct 2026
- **Also known as:** GHSA-w44p-jxhf-26w5

## What is CVE-2026-93849?

CVE-2026-93849 is a medium-severity vulnerability in Mattermost, published on 26 Oct 2026. 

### Official description

Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 Mattermost fail to apply allocation limits to the byte-string decode paths in its WebSocket msgpack decoder, which allows an authenticated remote attacker to cause excessive server memory allocation via a crafted binary WebSocket frame declaring a Bin32 payload length of up to 4,294,967,295 bytes.. Mattermost Advisory ID: MMSA-2026-00768

Weakness: CWE-789 (Memory Allocation with Excessive Size Value)

## Which versions are affected by CVE-2026-93849?


## How do I fix CVE-2026-93849?

No fix has been published for CVE-2026-93849 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-93849 being exploited?

There is no known exploitation of CVE-2026-93849 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93849 and fix it if it is affected.

What it is: CVE-2026-93849 is a medium-severity vulnerability in Mattermost, published on 26 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-93849 in the wild and no public exploit code.

Affected product: Mattermost. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-93849/ (Markdown: https://insights.sbomify.com/CVE-2026-93849/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93849
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93849
- OSV: https://osv.dev/vulnerability/CVE-2026-93849

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93849/
Summaries are generated and may contain mistakes; the official description above is the record.