How severe is CVE-2025-12419?

CVE-2025-12419 has a CVSS score of 9.9/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2025-12419?

CVE-2025-12419 affects the following packages: github.com/mattermost/mattermost/server/v8 (Go), github.com/mattermost/mattermost-server (Go), github.com/mattermost/mattermost-server (Go), github.com/mattermost/mattermost-server (Go), github.com/mattermost/mattermost-server (Go). Ecosystems affected: Go.

How do I fix CVE-2025-12419?

Update github.com/mattermost/mattermost/server/v8 to 8.0.0-20251028000919-d3ed703dc833 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-12419 is resolved across your whole dependency graph.

How do I detect CVE-2025-12419 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/mattermost/mattermost/server/v8, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-12419 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2025-12419 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-12419 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2025-12419?

CVE-2025-12419 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 31th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2025-12419?

CVE-2025-12419 is classified as CWE-303 (CWE-303). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-12419 published, and has it been updated?

CVE-2025-12419 was published on November 27, 2025 and was last updated on November 7, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

CRITICAL severity

CVE-2025-12419 — server

CRITICALFix: mattermost/mattermost#34296

CVE-2025-12419 is a critical-severity (CVSS 9.9) CWE-303 vulnerability in github.com/mattermost/mattermost/server/v8. A fix is available for github.com/mattermost/mattermost/server/v8 — see the affected versions and patch details below.

Account takeover on OAuth/OpenID-enabled servers

Also known asGHSA-3x39-62h4-f8j6GO-2025-4168

Published

Nov 27, 2025

Updated

Nov 7, 2026

Affected

5 pkgs

Patched

5 / 5

Exploits

None indexed

Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-12419.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs31th percentile — riskier than 31% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

5 pkgs affected

🐹github.com/mattermost/mattermost/server/v8🐹github.com/mattermost/mattermost-server🐹github.com/mattermost/mattermost-server🐹github.com/mattermost/mattermost-server🐹github.com/mattermost/mattermost-server

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Mattermost versions 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12, 11.0.x <= 11.0.3 fail to properly validate OAuth state tokens during OpenID Connect authentication which allows an authenticated attacker with team creation privileges to take over a user account via manipulation of authentication data during the OAuth completion flow. This requires email verification to be disabled (default: disabled), OAuth/OpenID Connect to be enabled, and the attacker to control two users in the SSO system with one of them never having logged into Mattermost.

Affected Packages

5 total 5 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/mattermost/mattermost/server/v8`	all versions	8.0.0-20251028000919-d3ed703dc833`go get github.com/mattermost/mattermost/server/v8@v8.0.0-20251028000919-d3ed703dc833`
🐹Go	`github.com/mattermost/mattermost-server`	≥ 10.12.0&&< 10.12.2	10.12.2`go get github.com/mattermost/mattermost-server@v10.12.2`
🐹Go	`github.com/mattermost/mattermost-server`	≥ 10.11.0&&< 10.11.5	10.11.5`go get github.com/mattermost/mattermost-server@v10.11.5`
🐹Go	`github.com/mattermost/mattermost-server`	≥ 10.5.0&&< 10.5.13	10.5.13`go get github.com/mattermost/mattermost-server@v10.5.13`
🐹Go	`github.com/mattermost/mattermost-server`	≥ 11.0.0&&< 11.0.4	11.0.4`go get github.com/mattermost/mattermost-server@v11.0.4`

Affected Products

1 product · 4 configurations

Application

mattermost servermattermost

≥ 11.0.0 && < 11.0.4

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/mattermost/mattermost/server/v8, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/mattermost/mattermost/server/v8 to 8.0.0-20251028000919-d3ed703dc833 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-12419 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2025-12419 in your dependencies?

Find it across Go, including transitive dependencies.

Scan my dependencies How O3 SCA works