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Vulnerability record · CVE-2026-44300 · published 15 September 2026

CVE-2026-44300: Improper input validation vulnerability

OpenCost provides cost monitoring for Kubernetes workloads and cloud costs. Prior to 1.121.0, the POST /serviceKey endpoint in pkg/costmodel/router.go allows a network client to invoke AddServiceKey without mandatory authentication and submit an arbitrary key form value that is written to the GCP service-account key.json file returned by GetGCPAuthSecretFilePath in core/pkg/env/core.go. The attacker controls the file contents but not the CONFIG_PATH-derived directory, the key.json filename, or the file mode. Replacing the credential contents can disrupt GCP cost collection or cause OpenCost to use attacker-selected credentials, and the wildcard Access-Control-Allow-Origin response permits browser-assisted requests when the service is reachable from a browser. This issue is fixed in version 1.121.0.

8.8 CVSS 4.0 High EPSS 0.75% · top 46.8% CWE-20 · Improper input validationCWE-309 · CWE-309 Received
8.8CVSS 4.0 base score
0.75%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
7References
15 Sep 2026Last modified by NVD

Description

OpenCost provides cost monitoring for Kubernetes workloads and cloud costs. Prior to 1.121.0, the POST /serviceKey endpoint in pkg/costmodel/router.go allows a network client to invoke AddServiceKey without mandatory authentication and submit an arbitrary key form value that is written to the GCP service-account key.json file returned by GetGCPAuthSecretFilePath in core/pkg/env/core.go. The attacker controls the file contents but not the CONFIG_PATH-derived directory, the key.json filename, or the file mode. Replacing the credential contents can disrupt GCP cost collection or cause OpenCost to use attacker-selected credentials, and the wildcard Access-Control-Allow-Origin response permits browser-assisted requests when the service is reachable from a browser. This issue is fixed in version 1.121.0.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/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:

References

LinkTags
https://github.com/opencost/opencost/commit/69430e7f627b3e62c8999312c06949267fab813a
https://github.com/opencost/opencost/commit/a49a25bc2e0d6e220a131a4dc58f38ebe6ae851b
https://github.com/opencost/opencost/pull/3651
https://github.com/opencost/opencost/pull/3910
https://github.com/opencost/opencost/releases/tag/v1.120.0
https://github.com/opencost/opencost/releases/tag/v1.121.0
https://github.com/opencost/opencost/security/advisories/GHSA-wmj8-9953-vff5

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Source: NIST National Vulnerability Database (record CVE-2026-44300), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.