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MEDIUM severity

Mattermost Exposure of Sensitive Information to an Unauthorized Actor vulnerabilityGHSA-63cv-4pc2-4fcf

MEDIUM

GHSA-63cv-4pc2-4fcf is a medium-severity (CVSS 5.3) Information Exposure vulnerability in github.com/mattermost/mattermost-server/v6. A fix is available for github.com/mattermost/mattermost-server/v6 — see the affected versions and patch details below.

Also known asBIT-mattermost-2023-6459CVE-2023-6459
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • 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 GHSA-63cv-4pc2-4fcf.

EPSS Exploitation Probability

via FIRST.org ↗
0.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs45th percentile — riskier than 45% of all scored CVEsHighest risk
0.00%0.34%0.69%1.03%0.5%0.5%May 26Sep 26Nov 26

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

2 pkgs affected
🐹github.com/mattermost/mattermost-server/v6🐹github.com/mattermost/mattermost/server/v8

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 is grouping calls in the /metrics endpoint by id and reports that id in the response. Since this id is the channelID, the public /metrics endpoint is revealing channelIDs.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/mattermost/mattermost-server/v6all versions7.8.14go get github.com/mattermost/mattermost-server/v6@v7.8.14
🐹Gogithub.com/mattermost/mattermost/server/v8all versions8.1.5go get github.com/mattermost/mattermost/server/v8@v8.1.5

Affected Products

1 product · 2 configurations
Application
mattermost servermattermost
≥ 8.0.0 && < 8.1.5
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/mattermost/mattermost-server/v6, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/mattermost/mattermost-server/v6 to 7.8.14 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-63cv-4pc2-4fcf is resolved across your whole dependency graph.

  3. Workarounds

    Assume what was exposed is already known: rotate any credential, token or key that the affected component could return, restrict the endpoint to callers that genuinely need it, and strip sensitive fields from responses and error output at the boundary rather than relying on the client not to read them.

Frequently Asked Questions

Mattermost is grouping calls in the /metrics endpoint by id and reports that id in the response. Since this id is the channelID, the public /metrics endpoint is revealing channelIDs.
O3 Security · Impact-Aware SCA

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Mattermost Exposure of Sensitive Information to an…