What is CVE-2026-13426?

CVE-2026-13426 is a medium-severity path traversal vulnerability in github.com/mattermost/mattermost/server/public (go), affecting versions < 0.1.22. It is fixed in 0.1.22. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.

How severe is CVE-2026-13426?

CVE-2026-13426 has a CVSS score of 5.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which versions of github.com/mattermost/mattermost/server/public are affected by CVE-2026-13426?

github.com/mattermost/mattermost/server/public (go) versions < 0.1.22 is affected.

Is there a fix for CVE-2026-13426?

Yes. CVE-2026-13426 is fixed in 0.1.22. Upgrade to this version or later.

Is CVE-2026-13426 exploitable, and should I be worried?

Whether CVE-2026-13426 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2026-13426 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

CVE-2026-13426

Q: How severe is CVE-2026-13426?

CVE-2026-13426 has a CVSS score of 5.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which versions of github.com/mattermost/mattermost/server/public are affected by CVE-2026-13426?

github.com/mattermost/mattermost/server/public (go) versions < 0.1.22 is affected.

Q: Is there a fix for CVE-2026-13426?

Yes. CVE-2026-13426 is fixed in 0.1.22. Upgrade to this version or later.

Q: Is CVE-2026-13426 exploitable, and should I be worried?

Whether CVE-2026-13426 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2026-13426 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2026-13426?

Upgrade github.com/mattermost/mattermost/server/public to 0.1.22 or later.

Summary

github.com/mattermost/mattermost/server/public vulnerable to path traversal in API route construction

The Mattermost Go module github.com/mattermost/mattermost/server/public versions < v0.1.22 fail to validate path parameters when constructing API route paths which allows an attacker to redirect API calls to unintended endpoints via crafted IDs containing path traversal components. Mattermost Advisory ID: MMSA-2025-00532

Impact

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2026-13426 has a CVSS score of 5.4 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.1.22); upgrading removes the vulnerable code path.

Affected versions

github.com/mattermost/mattermost/server/public (< 0.1.22)

Security releases

github.com/mattermost/mattermost/server/public → 0.1.22 (go)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

Upgrade github.com/mattermost/mattermost/server/public to 0.1.22 or later to resolve this vulnerability.

Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.

Frequently Asked Questions

What is CVE-2026-13426? CVE-2026-13426 is a medium-severity path traversal vulnerability in github.com/mattermost/mattermost/server/public (go), affecting versions < 0.1.22. It is fixed in 0.1.22. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
How severe is CVE-2026-13426? CVE-2026-13426 has a CVSS score of 5.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which versions of github.com/mattermost/mattermost/server/public are affected by CVE-2026-13426? github.com/mattermost/mattermost/server/public (go) versions < 0.1.22 is affected.
Is there a fix for CVE-2026-13426? Yes. CVE-2026-13426 is fixed in 0.1.22. Upgrade to this version or later.
Is CVE-2026-13426 exploitable, and should I be worried? Whether CVE-2026-13426 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2026-13426 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2026-13426? Upgrade github.com/mattermost/mattermost/server/public to 0.1.22 or later.