Mattermost Desktop App plugin popout scheme validation bypass
Priority LOW 13CWE-1287Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- Required
- Attack complexity
- High
- Impact type
- —
- Confidentiality · integrity · availability
- None · Low · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA.
Summary
Mattermost Desktop App versions <=6.2 6.2.2.0 fail to validate the URL scheme when checking whether a target URL is internal to the connected server, which allows a network-positioned attacker to load a plugin popout window over an insecure connection via a link using a downgraded URL scheme. Mattermost Advisory ID: MMSA-2026-00717
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00224 13th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 6.3.0, 6.2.3.0
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Mattermost | Mattermost | up to 6.2.2 | 6.3.0, 6.2.3.0 | Patch available | CNA |
- Mattermost VendorMattermost Affected up to 6.2.2 Fixed in 6.3.0, 6.2.3.0 Patch available CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mattermost:mattermost_desktop:*:*:*:*:*:*:*:* | 6.2.0 to before 6.2.3 | Vulnerable | Mattermost |
- cpe:2.3:a:mattermost:mattermost_desktop:*:*:*:*:*:*:*:* Versions 6.2.0 to before 6.2.3 Vulnerable ·Mattermost
Remediation
- Fix · CNA Mattermost (Mattermost) Fixed in 6.3.0, 6.2.3.0
Timeline
- 2026-10-02 Threatist record created from CVE-2026-75588
- 2026-10-03 Alias added: GHSA-p8rx-2r7q-5wfv
References
Advisory 1
More Mattermost Desktop vulnerabilities
- TI-2019-15074 An issue was discovered in Mattermost Desktop App before 4.3.0 on macOS. CVSS 3.1CRITICAL 9.8
- TI-2016-09099 An issue was discovered in Mattermost Desktop App before 3.4.0. CVSS 3.1CRITICAL 9.8
- TI-2019-15079 An issue was discovered in Mattermost Desktop App before 4.2.2. CVSS 3.1HIGH 8.8
- TI-2024-26542 RCE in desktop app in Windows by local attacker CVSS 3.1HIGH 7.8
- TI-2026-05712 Mattermost Desktop App fails to restrict the allow list of domains which NTLM credentials are passed CVSS 3.1HIGH 7.7
- TI-2026-00781 Arbitrary application execution via unvalidated server-controlled URLs in Help menu CVSS 3.1HIGH 7.6
Sources
- CVE-2026-75588 · CVE Program
- CVE-2026-75588 · NVD
- FIRST EPSS
- GHSA-p8rx-2r7q-5wfv · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences