CVE-2025-8402 Nil pointer dereference in bulk import crashes server
Medium 4.9
Published
Updated
Check this codebase for CVE-2025-8402 and fix it if it is affected.
What it is: CVE-2025-8402 is a medium-severity vulnerability in Mattermost Mattermost Server, published on 21 Aug 2025. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-8402 in the wild and no public exploit code.
Affected packages and fixed versions:
- github.com/mattermost/mattermost-server (Go): affected from 10.10.0; fixed in 10.10.1
- github.com/mattermost/mattermost-server (Go): affected from 10.10.0; fixed in 10.10.1
- github.com/mattermost/mattermost-server (Go): affected from 10.5.0; fixed in 10.5.9
- github.com/mattermost/mattermost-server (Go): affected from 10.5.0; fixed in 10.5.9
- github.com/mattermost/mattermost-server (Go): affected from 10.8.0; fixed in 10.8.4
- github.com/mattermost/mattermost-server (Go): affected from 10.8.0; fixed in 10.8.4
- github.com/mattermost/mattermost-server (Go): affected from 10.9.0; fixed in 10.9.4
- github.com/mattermost/mattermost-server (Go): affected from 10.9.0; fixed in 10.9.4
- github.com/mattermost/mattermost-server (Go): affected from 9.11.0; fixed in 9.11.18
- github.com/mattermost/mattermost-server (Go): affected from 9.11.0; fixed in 9.11.18
- github.com/mattermost/mattermost-server (Go): affected from 9.11.0+incompatible; fixed in 9.11.18+incompatible, 10.5.9+incompatible, 10.8.4+incompatible, 10.9.4+incompatible, 10.10.1+incompatible
- github.com/mattermost/mattermost-server/v5 (Go): affected all versions; no fix listed
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-2025-8402/ (Markdown: https://insights.sbomify.com/CVE-2025-8402/index.md)
A system administrator can crash the Mattermost server by providing invalid data to the bulk import feature due to a nil pointer dereference.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-8402?
CVE-2025-8402 is a medium-severity vulnerability in Mattermost Mattermost Server, published on 21 Aug 2025. An attacker needs administrator access to exploit it, with no action from the victim.
Official description
Mattermost versions 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 9.11.x <= 9.11.17, 10.10.x <= 10.10.0, 10.9.x <= 10.9.3 fail to validate import data which allows a system admin to crash the server via the bulk import feature.
Which versions are affected by CVE-2025-8402?
20 open source packages ship an affected version, including github.com/mattermost/mattermost-server, github.com/mattermost/mattermost-server/v5 and github.com/mattermost/mattermost-server/v6. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/mattermost/mattermost-server Go | From 10.10.0 | 10.10.1 |
github.com/mattermost/mattermost-server Go | From 10.10.0 | 10.10.1 |
github.com/mattermost/mattermost-server Go | From 10.5.0 | 10.5.9 |
github.com/mattermost/mattermost-server Go | From 10.5.0 | 10.5.9 |
github.com/mattermost/mattermost-server Go | From 10.8.0 | 10.8.4 |
github.com/mattermost/mattermost-server Go | From 10.8.0 | 10.8.4 |
14 more packages
github.com/mattermost/mattermost-server Go | From 10.9.0 | 10.9.4 |
github.com/mattermost/mattermost-server Go | From 10.9.0 | 10.9.4 |
github.com/mattermost/mattermost-server Go | From 9.11.0 | 9.11.18 |
github.com/mattermost/mattermost-server Go | From 9.11.0 | 9.11.18 |
github.com/mattermost/mattermost-server Go | From 9.11.0+incompatible | 9.11.18+incompatible, 10.5.9+incompatible, 10.8.4+incompatible, 10.9.4+incompatible, 10.10.1+incompatible |
github.com/mattermost/mattermost-server/v5 Go | All versions | None |
github.com/mattermost/mattermost-server/v5 Go | All versions to 5.39.3 | None |
github.com/mattermost/mattermost-server/v5 Go | All versions to 5.39.3 | None |
github.com/mattermost/mattermost-server/v6 Go | All versions | None |
github.com/mattermost/mattermost-server/v6 Go | All versions to 6.7.2 | None |
github.com/mattermost/mattermost-server/v6 Go | All versions to 6.7.2 | None |
github.com/mattermost/mattermost/server/v8 Go | All versions | None |
github.com/mattermost/mattermost/server/v8 Go | All versions | 8.0.0-20250708173752-d6b35c41f0ae5 |
github.com/mattermost/mattermost/server/v8 Go | All versions | 8.0.0-20250708173752-d6b35c41f0ae5 |
Products include Mattermost Mattermost Server.
How do I fix CVE-2025-8402?
Upgrade github.com/mattermost/mattermost-server to a fixed version for your release line: 10.10.1, 10.5.9, 10.8.4 or 10.9.4.
Is CVE-2025-8402 being exploited?
There is no known exploitation of CVE-2025-8402 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-h469-4fcf-p23h, GO-2025-3911.