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Suggestion detail

Untriaged
Permalink CVE-2026-4339
6.5 MEDIUM
  • CVSS version (CVSS): 3.1
  • Attack Vector (AV): Local (L)
  • Attack Complexity (AC): Low (L)
  • Privileges Required (PR): Low (L)
  • User Interaction (UI): None (N)
  • Scope (S): Changed (C)
  • Confidentiality (C): High (H)
  • Integrity (I): None (N)
  • Availability (A): None (N)
  • Modified Attack Vector (MAV): Local (L)
  • Modified Attack Complexity (MAC): Low (L)
  • Modified Privileges Required (MPR): Low (L)
  • Modified User Interaction (MUI): None (N)
  • Modified Confidentiality (MC): High (H)
  • Modified Scope (MS): Changed (C)
  • Modified Integrity (MI): None (N)
  • Modified Availability (MA): None (N)
created 2 weeks, 5 days ago Activity log
  • Created suggestion
SSRF via unvalidated attachment URLs in Mattermost Agents plugin MCP server

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

References

Affected products

Mattermost
  • ==11.5.7
  • ==11.7.0
  • =<10.11.18
  • ==10.11.19
  • =<11.5.6
  • =<11.6.3
  • ==11.6.4

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