Insecure Inter-Agent Communication

MCPHub, a centralized management hub for MCP servers, has an incomplete SSRF guard that fails to block IPv6 transition addresses like NAT64, 6to4, and Teredo. An attacker who can supply a URL for an MCP server connection can embed a private IPv4 address inside one of these IPv6 formats to bypass the filter and reach internal infrastructure. This is a classic SSRF filter evasion issue, patched in version 1.0.32.

Updated Sep 1, 2026

IBM Langflow versions 1.0.0 through 1.11.1 contain a critical flaw in the Agent-to-Agent (A2A) public endpoint that fails to properly enforce security restrictions, allowing a remote unauthenticated attacker to execute arbitrary code. With a CVSS score of 9.8, this is a severe, easily exploitable vulnerability that could grant full control of the affected system.

Updated Aug 29, 2026 · CVSS 9.8

pg-aiguide's MCP HTTP transport failed to enable a built-in DNS-rebinding protection option, allowing a malicious webpage to rebind a domain to the local server's address and issue unauthorized requests to the locally running MCP server via a victim's browser. This effectively bypasses the localhost trust boundary that MCP servers typically rely on for security. The issue was a configuration oversight rather than a missing SDK feature, and is fixed in version 0.5.1 by explicitly enabling the allow-list.

Updated Aug 29, 2026 · CVSS 6.8

mcp-go's HTTP transports failed to validate the Host header on loopback-bound requests, allowing a malicious webpage in a user's browser to use DNS rebinding to reach a local MCP server and invoke its tools or read its resources. This breaks the security assumption that only trusted local software can talk to a loopback-bound MCP server. The issue is fixed in 0.56.0 via strict host validation.

Updated Aug 29, 2026 · CVSS 6.8

Lightdash's scheduled delivery feature lets a user-supplied webhook URL be posted to directly by the GoogleChat and MicrosoftTeams clients without applying the existing SSRF protection used for MCP server URLs. This allows an authenticated user to force the server to make requests to internal, loopback, or cloud metadata endpoints and infer reachability from logged error responses. It is a classic SSRF issue in a webhook delivery path rather than an attack on agent reasoning or an AI-specific exploit, though it touches the same URL-validation utility used to secure MCP server connections.

Updated Aug 21, 2026 · CVSS 6.4

Jan's local API server (through v0.8.4) mishandles trusted host configuration, replacing user-defined allowed origins with a wildcard that reflects any origin while still allowing credentials. This lets a network-adjacent or DNS-rebinding attacker reach the unauthenticated OpenAI-compatible API to run inference, enumerate models, invoke MCP tools, and read cross-origin responses. Fixed in commit 3e1c1e7; upgrade is the primary remediation.

Updated Jul 24, 2026 · CVSS 6.3

Adversarial instructions planted in content processed by one agent can replicate into its outputs and infect downstream agents, spreading through normal inter-agent messaging the way the Morris II research worm spread through AI email assistants.

Updated Jul 3, 2026