Rob--W cors-anywhere instances configured as an open proxy allow unauthenticated external users to induce the server to make HTTP requests to arbitrary targets (SSRF). Because the proxy forwards requests and headers, an attacker can reach internal-only endpoints and link-local metadata services, retrieve instance role credentials or other sensitive metadata, and interact with internal APIs and services that are not intended to be internet-facing. The vulnerability is exploitable by sending crafted requests to the proxy with the target resource encoded in the URL; many cors-anywhere deployments forward arbitrary methods and headers (including PUT), which can permit exploitation of IMDSv2 workflows as well as access to internal management APIs. Successful exploitation can result in theft of cloud credentials, unauthorized access to internal services, remote code execution or privilege escalation (depending on reachable backends), data exfiltration, and full compromise of cloud resources. Mitigation includes: restricting the proxy to trusted origins or authentication, whitelisting allowed target hosts, preventing access to link-local and internal IP ranges, removing support for unsafe HTTP methods/headers, enabling cloud provider mitigations, and deploying network-level protections.
An attacker sends a crafted request to the cors-anywhere proxy, encoding the target resource in the URL. The proxy forwards the request along with headers to the specified target, enabling access to internal endpoints and instance metadata services (link-local metadata services). Many cors-anywhere deployments forward arbitrary HTTP methods (including PUT) and headers, allowing exploitation of IMDSv2 flows and access to internal management APIs. Successful exploitation allows retrieval of cloud instance role credentials or other sensitive metadata.
An attacker can obtain cloud credentials, gain unauthorized access to internal services and APIs, conduct data exfiltration, and depending on accessible backends — lead to RCE, privilege escalation, or complete takeover of cloud resources.
Restrict the proxy exclusively to trusted sources or require authentication, implement a whitelist of allowed target hosts, block access to link-local and internal IP address ranges, remove support for unsafe HTTP methods and headers, enable cloud provider protections (e.g., IMDSv2), and apply network-level protection. Apply patches available from the vendor according to references.
Cors-anywhere instances (by Rob--W) configured as an open proxy without restrictions on allowed sources or target hosts; versions indicated in vendor references
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X