CVE-2026-4339
- Source
- https://cve.org/CVERecord?id=CVE-2026-4339
- Import Source
- https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-4339.json
- JSON Data
- https://api.osv.dev/v1/vulns/CVE-2026-4339
- Published
- 2026-06-26T14:44:58.655Z
- Modified
- 2026-07-08T08:13:29.199224454Z
- Severity
-
- 6.5 (Medium) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N CVSS Calculator
- Summary
- SSRF via unvalidated attachment URLs in Mattermost Agents plugin MCP server
- Details
-
Mattermost versions 10.11.x <= 10.11.18, 11.6.x <= 11.6.3, 11.5.x <= 11.5.6 fail to validate attachment URLs against internal or private IP ranges in the Mattermost Agents plugin MCP server which allows an attacker with access to the MCP server in stdio mode to perform server-side request forgery (SSRF) and exfiltrate data from internal network services via supplying internal URLs as file attachments in post creation requests.. Mattermost Advisory ID: MMSA-2026-00635
- Database specific
{ "unresolved_ranges": [ { "source": "AFFECTED_FIELD", "extracted_events": [ { "introduced": "10.11.0" }, { "last_affected": "10.11.18" }, { "introduced": "11.6.0" }, { "last_affected": "11.6.3" }, { "introduced": "11.5.0" }, { "last_affected": "11.5.6" } ] } ], "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/4xxx/CVE-2026-4339.json", "cna_assigner": "Mattermost", "cwe_ids": [ "CWE-918" ] }- References
Affected packages
Git / github.com/mattermost/mattermost
Affected ranges
- Type
- GIT
- Repo
- https://github.com/mattermost/mattermost
- Events
- Database specific
{ "source": "CPE_RANGE", "cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*", "extracted_events": [ { "introduced": "10.11.0" }, { "fixed": "10.11.19" }, { "introduced": "11.5.0" }, { "fixed": "11.5.7" }, { "introduced": "11.6.0" }, { "fixed": "11.6.4" } ] }
Affected versions
@mattermost/client@10.*
@mattermost/client@10.11.0
@mattermost/types@10.*
@mattermost/types@10.11.0
mattermost-redux@10.*
mattermost-redux@10.11.0
v10.*
v10.11.0
v10.11.0-rc3
v10.11.1
v10.11.1-rc1
v10.11.10
v10.11.11
v10.11.11-rc1
v10.11.11-rc2
v10.11.12
v10.11.13
v10.11.13-rc1
v10.11.14
v10.11.14-rc1
v10.11.15
v10.11.15-rc1
v10.11.16
v10.11.17
v10.11.18
v10.11.19-rc1
v10.11.2
v10.11.2-rc1
v10.11.2-rc2
v10.11.3
v10.11.4
v10.11.4-rc1
v10.11.4-rc2
v10.11.4-rc3
v10.11.5
v10.11.6
v10.11.7
v10.11.8
v10.11.9
v10.11.9-rc1
v11.*
v11.5.0
v11.5.1
v11.5.2
v11.5.2-rc1
v11.5.2-rc2
v11.5.2-rc3
v11.5.3
v11.5.4
v11.5.5
v11.5.6
v11.6.0
v11.6.1
v11.6.1-rc1
v11.6.2
v11.6.3