How severe is CVE-2017-18896?

CVE-2017-18896 has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2017-18896?

CVE-2017-18896 affects the following packages: 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-2017-18896?

Update github.com/mattermost/mattermost-server to 4.1.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2017-18896 is resolved across your whole dependency graph.

How do I detect CVE-2017-18896 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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2017-18896 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-2017-18896 actively exploited in the wild?

No public exploit code has been indexed for CVE-2017-18896 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-2017-18896?

CVE-2017-18896 has an EPSS (Exploit Prediction Scoring System) score of 0.8%, placing it in the 56th 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-2017-18896?

CVE-2017-18896 is classified as CWE-732 (CWE-732). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2017-18896 published, and has it been updated?

CVE-2017-18896 was published on June 19, 2020 and was last updated on October 24, 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

MEDIUM severity

CVE-2017-18896 — mattermost-server

MEDIUMFix: mattermost/mattermost@3c34e2b

CVE-2017-18896 is a medium-severity (CVSS 5.3) CWE-732 vulnerability in github.com/mattermost/mattermost-server. A fix is available for github.com/mattermost/mattermost-server — see the affected versions and patch details below.

Mattermost Server allows attackers to log sensitive information via DEBUG REST API logging endpoint

Also known asGHSA-63wg-qmrv-7q66GO-2026-4299

Published

Jun 19, 2020

Updated

Oct 24, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Oct 29, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.8%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs56th percentile — riskier than 56% 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

3 pkgs affected

🐹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

An issue was discovered in Mattermost Server before 4.2.0, 4.1.1, and 4.0.5. It allows attackers to add DEBUG lines to the logs via a REST API version 3 logging endpoint.

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/mattermost/mattermost-server`	≥ 4.1.0&&< 4.1.1	4.1.1`go get github.com/mattermost/mattermost-server@v4.1.1`
🐹Go	`github.com/mattermost/mattermost-server`	all versions	4.0.5`go get github.com/mattermost/mattermost-server@v4.0.5`
🐹Go	`github.com/mattermost/mattermost-server`	≥ 4.2.0-rc1&&< 4.2.0	4.2.0`go get github.com/mattermost/mattermost-server@v4.2.0`

Affected Products

1 product · 6 configurations

Application

mattermost servermattermost

≥ 4.1.0 && < 4.1.1

1 version

4.2.0

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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/mattermost/mattermost-server to 4.1.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2017-18896 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

An issue was discovered in Mattermost Server before 4.2.0, 4.1.1, and 4.0.5. It allows attackers to add DEBUG lines to the logs via a REST API version 3 logging endpoint.

O3 Security · Impact-Aware SCA

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Find it across Go, including transitive dependencies.

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CVSS Score

5.3/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CWE Classification

CWE-732CWE-732

Weaponization

No Nuclei template, Metasploit module or public proof-of-concept found.

OpenSSF Scorecard

Package health score

mattermost

7.3/10

Dependency-Update-Tool10/10

Code-Review10/10

Maintained10/10

Branch-Protection4/10

Vulnerabilities0/10

Assessed Oct 28, 2026

Timeline

Disclosed

Jun 19, 2020

Last updated

Oct 24, 2026

Identifiers

CVE-2017-18896

GHSA-63wg-qmrv-7q66

GO-2026-4299

References

Advisorymattermost.com · security updates Advisorynvd.nist.gov · CVE 2017 18896 Webgithub.com · 3c34e2b2dcb0fde96a10e68d877aa7d0ab511669 Webgithub.com · 722fb1947a2e7395ccf16adce9206736d803a9f3 Webgithub.com · d38328976e2c8bb0fab91e656042a0d8ac37bc76 Webgithub.com · mattermost Webmattermost.com · security updates

Related vulnerabilities

This CVE is medium severity; 6 of 8 other CVEs affecting mattermost-server are rated as high or higher (top: high).

CVE-2026-5139CVE-2026-8074CVE-2026-9162CVE-2026-6673CVE-2026-6062CVE-2026-8823CVE-2026-6046CVE-2026-7387

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 24, 2026

CVE-2017-18896 — mattermost-server

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2017-18896 in your dependencies?