CVE-2026-108586 1mcp-app CVE debrief

Who should care

Defenders responsible for 1MCP Agent systems, security teams, and administrators should assess the exposure of their systems to this vulnerability and prioritize verification and remediation efforts.

Why it matters

CVE-2026-108586 is a medium-severity vulnerability in 1MCP Agent that allows authenticated clients to bypass OAuth tag-scope enforcement, potentially leading to unauthorized access to backend MCP servers.

• Authenticated attackers can list and invoke tools on backend MCP servers outside their granted scopes
• Defenders need to verify the OAuth tag-scope enforcement bypass vulnerability in 1MCP Agent versions 0.20.0 through 0.39.0
• Remediation requires updating 1MCP Agent configurations to prevent unauthorized access

Technical summary

The 1MCP Agent versions 0.20.0 through 0.39.0 contain an incorrect authorization vulnerability that allows authenticated clients to bypass OAuth tag-scope enforcement using negated advanced tag-filter expressions. This vulnerability can be exploited by attackers holding a single-tag token to list and invoke tools on backend MCP servers outside their granted scopes. The issue arises from the improper handling of advanced tag-filter expressions, which can be manipulated to bypass OAuth tag-scope enforcement. Defenders should prioritize verifying the OAuth tag-scope enforcement bypass vulnerability in 1MCP Agent versions 0.20.0 through 0.39.0 and assessing the exposure of their systems.

Defensive priority

Defenders should prioritize verifying the OAuth tag-scope enforcement bypass vulnerability in 1MCP Agent versions 0.20.0 through 0.39.0 and assessing the exposure of their systems.

Recommended defensive actions

• Verify the OAuth tag-scope enforcement bypass vulnerability in 1MCP Agent versions 0.20.0 through 0.39.0
• Assess the exposure of 1MCP Agent systems to this vulnerability
• Review and update 1MCP Agent configurations to prevent unauthorized access
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record and NVD entry provide details about the vulnerability, but the scope of affected systems and remediation steps require further verification from official sources. Affected product deployments need to be identified and verified for exposure. The 1MCP Agent GitHub repository and related documentation should be reviewed for additional context. Official advisories and CVE records should be consulted for the latest information on affected versions and remediation steps. The vulnerability's impact on backend MCP servers and 1

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.