How severe is CVE-2017-18908?

CVE-2017-18908 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2017-18908?

CVE-2017-18908 affects the following packages: github.com/mattermost/mattermost-server (Go), github.com/mattermost/mattermost-server (Go). Ecosystems affected: Go.

How do I fix CVE-2017-18908?

Update github.com/mattermost/mattermost-server to 3.9.1-rc1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2017-18908 is resolved across your whole dependency graph.

How do I detect CVE-2017-18908 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-2017-18908 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2017-18908 actively exploited in the wild?

No public exploit code has been indexed for CVE-2017-18908 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-2017-18908?

CVE-2017-18908 has an EPSS (Exploit Prediction Scoring System) score of 1.2%, placing it in the 68th 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-2017-18908?

CVE-2017-18908 is classified as Improper Authentication (CWE-287). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2017-18908 published, and has it been updated?

CVE-2017-18908 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

CRITICAL severity

CVE-2017-18908 — mattermost-server

CRITICALFix: mattermost/mattermost@5913939

CVE-2017-18908 is a critical-severity (CVSS 9.8) Improper Authentication 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 password reset email requests can be sent to attacker-provided email addresses

Also known asGHSA-34cx-hvm4-vx7jGO-2026-4476

Published

Jun 19, 2020

Updated

Oct 24, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs68th percentile — riskier than 68% 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

2 pkgs affected

🐹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 4.0.0, 3.10.1, and 3.9.1. A password reset request was sometimes sent to an attacker-provided e-mail address.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/mattermost/mattermost-server`	all versions	3.9.1-rc1`go get github.com/mattermost/mattermost-server@v3.9.1-rc1`
🐹Go	`github.com/mattermost/mattermost-server`	≥ 3.10.0&&< 3.10.1	3.10.1`go get github.com/mattermost/mattermost-server@v3.10.1`

Affected Products

1 product · 2 configurations

Application

mattermost servermattermost

≥ 3.10.0 && < 3.10.2

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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/mattermost/mattermost-server to 3.9.1-rc1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2017-18908 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

An issue was discovered in Mattermost Server before 4.0.0, 3.10.1, and 3.9.1. A password reset request was sometimes sent to an attacker-provided e-mail address.

O3 Security · Impact-Aware SCA

Is CVE-2017-18908 in your dependencies?

Find it across Go, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

9.8/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Raw vector

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

CWE Classification

CWE-287Improper Authentication

Weaponization

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

OpenSSF Scorecard

Package health score

mattermost

7.3/10

Maintained10/10

Dependency-Update-Tool10/10

Code-Review10/10

Branch-Protection4/10

Vulnerabilities0/10

Assessed Nov 8, 2026

Timeline

Disclosed

Jun 19, 2020

Last updated

Oct 24, 2026

Identifiers

CVE-2017-18908

GHSA-34cx-hvm4-vx7j

GO-2026-4476

References

Advisorymattermost.com · security updates Advisorynvd.nist.gov · CVE 2017 18908 Webgithub.com · 59139390ae927af2e879dbacfe4dadb1adac97c0 Webgithub.com · d3bc11be3acd3a73e6358d958b91427e2584ea71 Webgithub.com · e5065cf7575ee05c040945a4b00b7fd90bf39b83 Webmattermost.com · security updates Packagegithub.com · mattermost

Related vulnerabilities

This CVE is critical severity — higher than any of the other 8 CVEs affecting mattermost-server (highest there: 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-2017-18908 — 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-2017-18908 in your dependencies?