How severe is CVE-2026-13426?

CVE-2026-13426 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2026-13426 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (10th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-13426?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-13426 have an EU (EUVD) identifier?

Yes. CVE-2026-13426 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-39661.

When was CVE-2026-13426 published?

CVE-2026-13426 was published on 2026-06-26.

CVE-2026-13426

CVE-2026-13426 is a medium-severity vulnerability with a CVSS 3.x base score of 5.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-22.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
EPSS exploit prediction: 0% (10th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-39661
Weakness: CWE-22
Published: 2026-06-26
Last modified: 2026-06-26

Description

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

Frequently asked questions

What is CVE-2026-13426?: 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
How severe is CVE-2026-13426?: CVE-2026-13426 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-13426 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (10th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-13426?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-13426 have an EU (EUVD) identifier?: Yes. CVE-2026-13426 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-39661.
When was CVE-2026-13426 published?: CVE-2026-13426 was published on 2026-06-26.

References

https://mattermost.com/security-updates

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