How severe is CVE-2024-39777?

CVE-2024-39777 has a CVSS 3.x base score of 8.7, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2024-39777 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (28th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2024-39777?

CVE-2024-39777 primarily affects Mattermost. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2024-39777?

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-2024-39777 have an EU (EUVD) identifier?

Yes. CVE-2024-39777 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2024-2628.

When was CVE-2024-39777 published?

CVE-2024-39777 was published on 2024-08-01 and last updated on 2026-06-17.

CVE-2024-39777

CVE-2024-39777 is a high-severity vulnerability in Mattermost with a CVSS 3.x base score of 8.7. 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-284.

Key facts

Severity: High (CVSS 3.x base score 8.7)
EPSS exploit prediction: 0% (28th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2024-2628
Weakness: CWE-284
Affected product: Mattermost
Published: 2024-08-01
Last modified: 2026-06-17

Description

Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to disallow unsolicited invites to expose access to local channels, when shared channels are enabled, which allows a malicious remote to send an invite with the ID of an existing local channel, and that local channel will then become shared without the consent of the local admin.

Frequently asked questions

What is CVE-2024-39777?: Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to disallow unsolicited invites to expose access to local channels, when shared channels are enabled, which allows a malicious remote to send an invite with the ID of an existing local channel, and that local channel will then become shared without the consent of the local admin.
How severe is CVE-2024-39777?: CVE-2024-39777 has a CVSS 3.x base score of 8.7, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2024-39777 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (28th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2024-39777?: CVE-2024-39777 primarily affects Mattermost. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2024-39777?: 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-2024-39777 have an EU (EUVD) identifier?: Yes. CVE-2024-39777 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2024-2628.
When was CVE-2024-39777 published?: CVE-2024-39777 was published on 2024-08-01 and last updated on 2026-06-17.

References

https://mattermost.com/security-updates

Affected products (2)

cpe:2.3:a:mattermost:mattermost:*:*:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost:9.9.0:*:*:*:*:*:*:*

More vulnerabilities in Mattermost

CVE-2019-20851 — Critical (CVSS 9.1): An issue was discovered in Mattermost Mobile Apps before 1.26.0. An attacker can use directory traversal with the Video…
CVE-2024-39274 — High (CVSS 8.7): Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to properly validate…
CVE-2024-39830 — High (CVSS 8.1): Mattermost versions 9.8.x <= 9.8.0, 9.7.x <= 9.7.4, 9.6.x <= 9.6.2 and 9.5.x <= 9.5.5, when shared channels are…
CVE-2023-3615 — High (CVSS 8.1): Mattermost iOS app fails to properly validate the server certificate while initializing the TLS connection allowing a…
CVE-2020-13891 — High (CVSS 7.5): An issue was discovered in Mattermost Mobile Apps before 1.31.2 on iOS. Unintended third-party servers could sometimes…
CVE-2024-36492 — High (CVSS 7.4): Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5, 9.8.x <= 9.8.1 fail to disallow the modification of…

All CVEs affecting Mattermost →

Other CWE-284 (Improper Access Control) vulnerabilities

CVE-2026-50746 — Critical (CVSS 10.0): A malicious actor with access to the network could exploit an Improper Access Control vulnerability found in UniFi…
CVE-2026-46978 — Critical (CVSS 10.0): Vulnerability in the Oracle Solaris product of Oracle Systems (component: Remote Administration Daemon). The…
CVE-2026-35308 — Critical (CVSS 10.0): Vulnerability in the Oracle Coherence product of Oracle Fusion Middleware (component: Centralized Third Party Jars).…
CVE-2026-35307 — Critical (CVSS 10.0): Vulnerability in the Oracle Coherence product of Oracle Fusion Middleware (component: Core). Supported versions that…
CVE-2026-46695 — Critical (CVSS 10.0): Boxlite is a sandbox service that allows users to create lightweight virtual machines (Boxes) and launch OCI containers…
CVE-2026-46840 — Critical (CVSS 10.0): Vulnerability in Oracle REST Data Services (component: Backend-as-a-Service). Supported versions that are affected are…

Browse all CWE-284 (Improper Access Control) vulnerabilities →