CVE-2017-18883 Mattermost Server has low entropy for authorization data as an OAuth 2.0 Service Provider
Critical 9.1
Published
Updated
Check this codebase for CVE-2017-18883 and fix it if it is affected.
What it is: CVE-2017-18883 is a critical vulnerability in Mattermost Mattermost Server, published on 19 Jun 2020.
Exploitation: There is no known exploitation of CVE-2017-18883 in the wild and no public exploit code.
Affected packages and fixed versions:
- github.com/mattermost/mattermost-server (Go): affected all versions; fixed in 4.1.2+incompatible, 4.2.1+incompatible, 4.3.0+incompatible
- github.com/mattermost/mattermost-server (Go): affected all versions; fixed in 4.1.2
- github.com/mattermost/mattermost-server (Go): affected all versions; fixed in 4.1.2
- github.com/mattermost/mattermost-server (Go): affected from 4.2.0-rc1; fixed in 4.2.1
- github.com/mattermost/mattermost-server (Go): affected from 4.2.0-rc1; fixed in 4.2.1
- github.com/mattermost/mattermost-server (Go): affected from 4.3.0-rc1; fixed in 4.3.0
- github.com/mattermost/mattermost-server (Go): affected from 4.3.0-rc1; fixed in 4.3.0
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-2017-18883/ (Markdown: https://insights.sbomify.com/CVE-2017-18883/index.md)
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2017-18883?
CVE-2017-18883 is a critical vulnerability in Mattermost Mattermost Server, published on 19 Jun 2020.
Official description
An issue was discovered in Mattermost Server before 4.3.0, 4.2.1, and 4.1.2, when serving as an OAuth 2.0 Service Provider. There is low entropy for authorization data.
Weakness: CWE-331
Which versions are affected by CVE-2017-18883?
7 open source packages ship an affected version, including github.com/mattermost/mattermost-server. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/mattermost/mattermost-server Go | All versions | 4.1.2+incompatible, 4.2.1+incompatible, 4.3.0+incompatible |
github.com/mattermost/mattermost-server Go | All versions | 4.1.2 |
github.com/mattermost/mattermost-server Go | All versions | 4.1.2 |
github.com/mattermost/mattermost-server Go | From 4.2.0-rc1 | 4.2.1 |
github.com/mattermost/mattermost-server Go | From 4.2.0-rc1 | 4.2.1 |
github.com/mattermost/mattermost-server Go | From 4.3.0-rc1 | 4.3.0 |
1 more packages
github.com/mattermost/mattermost-server Go | From 4.3.0-rc1 | 4.3.0 |
Products include Mattermost Mattermost Server.
How do I fix CVE-2017-18883?
Upgrade github.com/mattermost/mattermost-server to a fixed version for your release line: 4.1.2+incompatible, 4.2.1+incompatible, 4.3.0+incompatible or 4.1.2.
Is CVE-2017-18883 being exploited?
There is no known exploitation of CVE-2017-18883 in the wild and no public exploit code.
Other vulnerabilities in Mattermost Mattermost Server
- CVE-2025-12419 Account takeover on OAuth/OpenID-enabled servers
- CVE-2025-12421 Account Takeover via Code Exchange Endpoint
- CVE-2025-4981 Path Traversal Leading to RCE by Any Authenticated Mattermost User
- CVE-2025-20051 Arbitrary file read via block duplication in Mattermost Boards
- CVE-2025-25279 Arbitrary file read in Mattermost Boards via import & export board archive
Sources
Also known as GHSA-w8cc-3h7q-jhc3, GO-2025-4198.