How severe is GHSA-498j-wxww-j897?

GHSA-498j-wxww-j897 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-498j-wxww-j897?

GHSA-498j-wxww-j897 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 GHSA-498j-wxww-j897?

Update github.com/mattermost/mattermost-server to 4.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-498j-wxww-j897 is resolved across your whole dependency graph.

How do I detect GHSA-498j-wxww-j897 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 GHSA-498j-wxww-j897 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is GHSA-498j-wxww-j897 actively exploited in the wild?

No public exploit code has been indexed for GHSA-498j-wxww-j897 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 GHSA-498j-wxww-j897?

GHSA-498j-wxww-j897 has an EPSS (Exploit Prediction Scoring System) score of 0.7%, placing it in the 51th 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 GHSA-498j-wxww-j897?

GHSA-498j-wxww-j897 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was GHSA-498j-wxww-j897 published, and has it been updated?

GHSA-498j-wxww-j897 was published on May 24, 2022 and was last updated on December 9, 2025. 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

GHSA-498j-wxww-j897 — mattermost-server

MEDIUM

GHSA-498j-wxww-j897 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) 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 is vulnerable to XSS through author_link field in Slack attachments

Also known asCVE-2017-18879GO-2025-4189

Published

May 24, 2022

Updated

Dec 9, 2025

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Sep 26, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.7%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs51th percentile — riskier than 51% of all scored CVEsHighest risk

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

How urgent is this, really

GHSA-498j-wxww-j897 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

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 4.3.0, 4.2.1, and 4.1.2. XSS could occur via the author_link field of a Slack attachment.

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/mattermost/mattermost-server`	all versions	4.1.2`go get github.com/mattermost/mattermost-server@v4.1.2`
🐹Go	`github.com/mattermost/mattermost-server`	≥ 4.2.0&&< 4.2.1	4.2.1`go get github.com/mattermost/mattermost-server@v4.2.1`
🐹Go	`github.com/mattermost/mattermost-server`	≥ 4.3.0-rc1&&< 4.3.0	4.3.0`go get github.com/mattermost/mattermost-server@v4.3.0`

Affected Products

1 product · 6 configurations

Application

mattermost servermattermost

≥ 4.2.0 && < 4.2.1

1 version

4.3.0

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 4.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-498j-wxww-j897 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

An issue was discovered in Mattermost Server before 4.3.0, 4.2.1, and 4.1.2. XSS could occur via the author_link field of a Slack attachment.

O3 Security · Impact-Aware SCA

Is GHSA-498j-wxww-j897 in your dependencies?

Find it across Go, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

6.1/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Raw vector

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

CWE Classification

CWE-79Cross-site Scripting (XSS)

Weaponization

No known public exploit tooling found.

OpenSSF Scorecard

Package health score

mattermost

7.3/10

Code-Review10/10

Maintained10/10

Dependency-Update-Tool10/10

Vulnerabilities0/10

Branch-Protection4/10

Assessed Sep 26, 2026

Timeline

Disclosed

May 24, 2022

Last updated

Dec 9, 2025

Identifiers

GHSA-498j-wxww-j897

GO-2025-4189

References

Advisorynvd.nist.gov Webmattermost.com Packagegithub.com

Related vulnerabilities

This CVE is medium severity; 7 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-2026-6046CVE-2026-7387CVE-2026-6961

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedDec 9, 2025