CVE-2026-108859

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{"bugzilla": {"description": "github.com/mark3labs/mcp-go: mcp-go: Denial of Service via unbounded HTTP request body buffering", "id": "2549285", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2549285"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.5", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-770", "details": ["mcp-go through 1.2.1 contains a denial of service vulnerability in StreamableHTTPServer.ServeHTTP that allows remote unauthenticated attackers to exhaust memory by sending oversized POST bodies. Attackers can send arbitrarily large or many concurrent POST requests, read fully via io.ReadAll before validation, to degrade or OOM-kill the server process.", "A flaw was found in mcp-go. The HTTP server implementation does not restrict the size of incoming HTTP POST request bodies before buffering them into memory. A remote, unauthenticated attacker can exploit this vulnerability by sending excessively large or multiple concurrent requests, causing memory exhaustion and leading to a Denial of Service (DoS) when the server crashes."], "mitigation": {"lang": "en:us", "value": "Restrict network exposure of the affected service to trusted clients or place it behind an intermediate reverse proxy or ingress controller that enforces strict HTTP request body size limits.\n1. Firewall configuration (for standalone host deployments):\nLimit access to the listening port to trusted subnets:\n```\nfirewall-cmd --permanent --zone=trusted --add-source=<TRUSTED_IP_OR_CIDR>\nfirewall-cmd --reload\n```\n2. OpenShift / Kubernetes environments:\nApply an OpenShift NetworkPolicy to restrict ingress traffic targeting the affected pods exclusively to authorized namespaces or ingress components. Additionally, configure ingress controllers or reverse proxies to limit maximum client request body sizes, dropping oversized POST requests before they reach backend services.\nCaveats:\nRestricting access to trusted networks will prevent unauthorized or external clients from accessing the service. Setting strict payload thresholds at the proxy layer may reject legitimate client requests that exceed the defined maximum size.\nWarning:\nRunning `firewall-cmd --reload` reloads active firewall configurations and can temporarily disrupt existing network connections."}, "name": "CVE-2026-108859", "package_state": [{"cpe": "cpe:/a:redhat:connectivity_link:1", "fix_state": "Affected", "package_name": "rhcl-tech-preview/mcp-gateway-rhel9", "product_name": "Red Hat Connectivity Link 1"}, {"cpe": "cpe:/a:redhat:connectivity_link:1", "fix_state": "Affected", "package_name": "rhcl-tech-preview/mcp-gateway-rhel9-operator", "product_name": "Red Hat Connectivity Link 1"}, {"cpe": "cpe:/a:redhat:hummingbird:1", "fix_state": "Affected", "package_name": "tempo2.10", "product_name": "Red Hat Hardened Images"}, {"cpe": "cpe:/a:redhat:hummingbird:1", "fix_state": "Affected", "package_name": "tempo3.0", "product_name": "Red Hat Hardened Images"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Affected", "package_name": "rhoai/rhai-cli-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_distributed_tracing:3", "fix_state": "Affected", "package_name": "rhosdt/tempo-query-rhel9", "product_name": "Red Hat OpenShift distributed tracing 3"}, {"cpe": "cpe:/a:redhat:openshift_distributed_tracing:3", "fix_state": "Affected", "package_name": "rhosdt/tempo-rhel9", "product_name": "Red Hat OpenShift distributed tracing 3"}], "public_date": "2026-10-11T13:26:06Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-108859\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-108859\nhttps://github.com/mark3labs/mcp-go\nhttps://github.com/mark3labs/mcp-go/blob/90d247ed8d45cbb7d71d9a95e112789b78760443/server/streamable_http.go#L405-L411\nhttps://hackmd.io/@1ExmmukzRMWN7B4gQ4W-4Q/mark3labs-mcp-go-streamable-http-unbounded-body\nhttps://www.vulncheck.com/advisories/mcp-go-through-1.2.1-denial-of-service-via-unbounded-post-body-buffering"], "statement": "This vulnerability is rated as having an Important severity because an unauthenticated remote attacker can cause an immediate denial of service by exhausting host memory without requiring privileges or user interaction. In affected Red Hat products, such as Red Hat OpenShift distributed tracing and Red Hat Connectivity Link, applications exposing the streamable HTTP endpoint to untrusted network traffic can be terminated by out-of-memory errors when processing oversized payloads. The vulnerability solely impacts service availability, with no compromise to data confidentiality or integrity.", "threat_severity": "Important"}

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