CVE-2026-1046
Mattermost Desktop 5.13.2 – 5.13.3
Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:LSummary
CVE-2026-1046 is a high-severity Improper Authorization in Handler for Custom URL Scheme (CWE-939) vulnerability in Mattermost Mattermost Desktop. Its CVSS base score is 7.6 (High).
Operationally, ranked at the 15th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and AC-6 (Least Privilege) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-1046 is a vulnerability in the Mattermost Desktop App affecting versions <=6.0, 6.2.0, and 5.2.13.0. The app fails to validate help links, which enables a malicious Mattermost server to execute arbitrary executables on a user's system when the user clicks on certain items in the Help menu. Published on 2026-02-16, the issue is rated 7.6 on the CVSS v3.1 scale (AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:L) and is associated with CWE-939.
An attacker who controls a Mattermost server can exploit this vulnerability against users connected to that server. Exploitation requires low privileges (PR:L) on the server side, user interaction (UI:R) by clicking Help menu items, and occurs over the network (AV:N). Successful exploitation allows execution of arbitrary executables on the victim's system, potentially leading to high confidentiality impacts and low availability disruption, with a scope change due to the privileged execution context.
Mattermost Advisory ID MMSA-2026-00577 provides details on mitigation. Security practitioners should refer to https://mattermost.com/security-updates for patch information and remediation guidance.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-6090
Vulnerability Data
Mattermost Desktop App versions <=6.0 6.2.0 5.2.13.0 fail to validate help links which allows a malicious Mattermost server to execute arbitrary executables on a user’s system via the user clicking on certain items in the Help menu Mattermost Advisory ID:…
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MMSA-2026-00577
- CWE(s)
Related Threats
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Access enforcement directly stops unauthorized actors from invoking the custom URL handler by requiring approved authorizations for that entry point.
Least privilege limits the authorizations granted to the handler, reducing the chance that any actor can invoke it without restriction.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Defining, enforcing, and reviewing access permissions directly addresses the missing authorization checks for custom URL scheme handlers.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can discover missing authorization checks, but does not itself implement the required controls.
Enforces explicit authorization checks on which actors may invoke handlers, directly addressing the missing restriction on custom-URL-scheme access.
High-level access-control policy provides governance context but does not prescribe the technical authorization logic needed for URL-scheme handlers.
Requires security requirements that define which callers are permitted to trigger custom URL handlers, mitigating the authorization gap.
Mandates secure coding practices that include proper authorization checks before executing actions triggered by custom URL schemes.