# CVE-2026-28741: CSRF Protection Bypass Allows Updating a User's Authentication Method > Attackers can bypass CSRF protection to change a user's authentication method, potentially leading to account takeover. - **Severity:** Medium 6.8 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** A user has to click or open something - **Fix available:** Yes - **Published:** 15 Apr 2026 - **Updated:** 15 Apr 2026 - **Also known as:** GHSA-m7cf-4gh2-v4qg, GO-2026-5495 ## What is CVE-2026-28741? CVE-2026-28741 is a medium-severity vulnerability in Mattermost Mattermost Server, published on 15 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link. ### Official 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 Weakness: CWE-352 (Cross-Site Request Forgery) ## Which versions are affected by CVE-2026-28741? 12 open source packages ship an affected version, including github.com/mattermost/mattermost/server/v8, github.com/mattermost/mattermost-server and github.com/mattermost/mattermost-server/v5. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `github.com/mattermost/mattermost/server/v8` | Go | From 11.3.0-rc1 | 11.3.3 | | `github.com/mattermost/mattermost/server/v8` | Go | From 11.3.0-rc1 | 11.3.3 | | `github.com/mattermost/mattermost/server/v8` | Go | From 11.4.0-rc1 | 11.4.3 | | `github.com/mattermost/mattermost/server/v8` | Go | From 11.4.0-rc1 | 11.4.3 | | `github.com/mattermost/mattermost/server/v8` | Go | From 11.5.0-rc1 | 11.5.0 | | `github.com/mattermost/mattermost/server/v8` | Go | From 11.5.0-rc1 | 11.5.0 | | `github.com/mattermost/mattermost/server/v8` | Go | From 8.0.0-20250721062209-4952acea88ce | 8.0.0-20260220133927-c29cf05d40f8 | | `github.com/mattermost/mattermost/server/v8` | Go | From 8.0.0-20250721062209-4952acea88ce | 8.0.0-20260220133927-c29cf05d40f8 | | `github.com/mattermost/mattermost/server/v8` | Go | From 8.0.0-20250721062209-4952acea88ce | 8.0.0-20260220133927-c29cf05d40f8 | | `github.com/mattermost/mattermost-server` | Go | From 11.3.0-rc1+incompatible | 11.3.3+incompatible, 11.4.3+incompatible, 11.5.0+incompatible | | `github.com/mattermost/mattermost-server/v5` | Go | All versions | None | | `github.com/mattermost/mattermost-server/v6` | Go | All versions | None | Products: Mattermost Mattermost Server. ## How do I fix CVE-2026-28741? Upgrade github.com/mattermost/mattermost/server/v8 to a fixed version for your release line: 11.3.3, 11.4.3, 11.5.0 or 8.0.0-20260220133927-c29cf05d40f8. ## Is CVE-2026-28741 being exploited? There is no known exploitation of CVE-2026-28741 in the wild and no public exploit code. ## Other vulnerabilities in Mattermost Mattermost Server - [CVE-2025-12419](https://insights.sbomify.com/CVE-2025-12419/): Account takeover on OAuth/OpenID-enabled servers (critical 9.9) - [CVE-2025-12421](https://insights.sbomify.com/CVE-2025-12421/): Account Takeover via Code Exchange Endpoint (critical 9.9) - [CVE-2025-4981](https://insights.sbomify.com/CVE-2025-4981/): Path Traversal Leading to RCE by Any Authenticated Mattermost User (critical 9.9) - [CVE-2025-20051](https://insights.sbomify.com/CVE-2025-20051/): Arbitrary file read via block duplication in Mattermost Boards (critical 9.9) - [CVE-2025-25279](https://insights.sbomify.com/CVE-2025-25279/): Arbitrary file read in Mattermost Boards via import & export board archive (critical 9.9) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-28741 and fix it if it is affected. What it is: CVE-2026-28741 is a medium-severity vulnerability in Mattermost Mattermost Server, published on 15 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link. Exploitation: There is no known exploitation of CVE-2026-28741 in the wild and no public exploit code. Affected packages and fixed versions: - github.com/mattermost/mattermost/server/v8 (Go): affected from 11.3.0-rc1; fixed in 11.3.3 - github.com/mattermost/mattermost/server/v8 (Go): affected from 11.3.0-rc1; fixed in 11.3.3 - github.com/mattermost/mattermost/server/v8 (Go): affected from 11.4.0-rc1; fixed in 11.4.3 - github.com/mattermost/mattermost/server/v8 (Go): affected from 11.4.0-rc1; fixed in 11.4.3 - github.com/mattermost/mattermost/server/v8 (Go): affected from 11.5.0-rc1; fixed in 11.5.0 - github.com/mattermost/mattermost/server/v8 (Go): affected from 11.5.0-rc1; fixed in 11.5.0 - github.com/mattermost/mattermost/server/v8 (Go): affected from 8.0.0-20250721062209-4952acea88ce; fixed in 8.0.0-20260220133927-c29cf05d40f8 - github.com/mattermost/mattermost/server/v8 (Go): affected from 8.0.0-20250721062209-4952acea88ce; fixed in 8.0.0-20260220133927-c29cf05d40f8 - github.com/mattermost/mattermost/server/v8 (Go): affected from 8.0.0-20250721062209-4952acea88ce; fixed in 8.0.0-20260220133927-c29cf05d40f8 - github.com/mattermost/mattermost-server (Go): affected from 11.3.0-rc1+incompatible; fixed in 11.3.3+incompatible, 11.4.3+incompatible, 11.5.0+incompatible - github.com/mattermost/mattermost-server/v5 (Go): affected all versions; no fix listed - github.com/mattermost/mattermost-server/v6 (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-2026-28741/ (Markdown: https://insights.sbomify.com/CVE-2026-28741/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-28741 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-28741 - OSV: https://osv.dev/vulnerability/CVE-2026-28741 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-28741/ Summaries are generated and may contain mistakes; the official description above is the record.