OpenCost prior to version 1.121.0 allows unauthenticated GET requests to the /helmValues endpoint, exposing the base64‑decoded HELM_VALUES environment variable that contains cloud provider credentials. Additionally, when the ADMIN_TOKEN environment variable is unset, the adminAuthMiddleware fails open, permitting unauthenticated attackers to submit POST requests to /serviceKey and modify Google Cloud Platform service account keys so that billing calls can be redirected. The result is the theft of privileged cloud credentials and a potential administrative bypass that could lead to unauthorized billing and data access. This weakness is identified as CWE‑306, missing authentication.

Products affected are OpenCost from the OpenCost vendor. Any installation of OpenCost with a version earlier than 1.121.0, including releases such as 1.120.x and earlier, is vulnerable. The issue was fixed in OpenCost release core/v1.121.0.

The CVSS score of 8.7 categorizes this flaw as a high‑severity vulnerability with widespread impact. The EPSS score of < 1% indicates a very low but non‑zero exploitation probability. The lack of authentication on the /helmValues and /serviceKey endpoints means an attacker who can reach the OpenCost service over the network can exploit this flaw without additional privileges. The vulnerability is not listed in CISA KEV, so no known active exploit is documented in that catalog; however, the straightforward nature of the attack vector makes it a likely candidate for exploitation by malicious actors.