How severe is CVE-2026-3524?

CVE-2026-3524 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-3524 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (31st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-3524?

CVE-2026-3524 affects Mattermost Legal Hold. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-3524?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-3524 have an EU (EUVD) identifier?

Yes. CVE-2026-3524 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19231.

When was CVE-2026-3524 published?

CVE-2026-3524 was published on 2026-04-06 and last updated on 2026-08-06.

CVE-2026-3524

CVE-2026-3524 is a high-severity vulnerability in Mattermost Legal Hold with a CVSS 3.x base score of 8.8. 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-862.

Key facts

Severity: High (CVSS 3.x base score 8.8)
EPSS exploit prediction: 0% (31st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-19231
Weakness: CWE-862
Affected product: Mattermost Legal Hold
Published: 2026-04-06
Last modified: 2026-08-06

Description

Mattermost Plugin Legal Hold versions <=1.1.4 fail to halt request processing after a failed authorization check in ServeHTTP which allows an authenticated attacker to access, create, download, and delete legal hold data via crafted API requests to the plugin's endpoints. Mattermost Advisory ID: MMSA-2026-00621

Frequently asked questions

What is CVE-2026-3524?: Mattermost Plugin Legal Hold versions <=1.1.4 fail to halt request processing after a failed authorization check in ServeHTTP which allows an authenticated attacker to access, create, download, and delete legal hold data via crafted API requests to the plugin's endpoints. Mattermost Advisory ID: MMSA-2026-00621
How severe is CVE-2026-3524?: CVE-2026-3524 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-3524 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (31st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-3524?: CVE-2026-3524 affects Mattermost Legal Hold. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-3524?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-3524 have an EU (EUVD) identifier?: Yes. CVE-2026-3524 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-19231.
When was CVE-2026-3524 published?: CVE-2026-3524 was published on 2026-04-06 and last updated on 2026-08-06.

References

https://mattermost.com/security-updates

Affected products (1)

cpe:2.3:a:mattermost:legal_hold:*:*:*:*:*:mattermost:*:*

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