OpenCost ServiceKey Endpoint Unauthorized Credential Overwrite/Injection

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.8 · 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 · score source

EPSS

• CVE-2026-44300: 0.75% estimated exploitation activity in the next 30 days; percentile 55.10 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary OpenCost contains an unauthenticated file write vulnerability in the /serviceKey endpoint that allows remote attackers to overwrite the GCP service account key file without authentication. This can lead to service disruption, credential theft, and potential privilege escalation within Kubernetes clusters. --- Affected Versions - OpenCost: All versions up to and including the latest release - Vulnerable File: pkg/costmodel/router.go (lines 365-379) - Vulnerable Endpoint: POST /serviceKey --- Vulnerability Details Root Cause The AddServiceKey function in pkg/costmodel/router.go accepts user-supplied data via POST request and writes it directly to a file without any authentication or input validation: File Path Determination (core/pkg/env/core.go): Security Issues 1. No Authentication: Any network-accessible client can invoke the endpoint 2. No Input Validation: User input is not validated as a valid GCP service account key 3. Overly Permissive CORS: Access-Control-Allow-Origin:…

Published by the source

14 Jul 2026, 17:07 UTC

Last modified by the source

14 Jul 2026, 17:19 UTC

Source last checked

26 Oct 2026, 15:24 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-wmj8-9953-vff5

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# Patch Next advisory brief: CVE-2026-44300

Advisory: OpenCost ServiceKey Endpoint Unauthorized Credential Overwrite/Injection
IDs: CVE-2026-44300, GHSA-wmj8-9953-vff5
Record: https://patchnext.com/advisories/cve-2026-44300 (revision 1, source checked 26 Oct 2026, 15:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/opencost/opencost 1.119.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/opencost/opencost: affected < 1.119.1; fixed in 1.119.1

## Suggested inspection (read-only)
- Go github.com/opencost/opencost: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/opencost/opencost.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-wmj8-9953-vff5 (GitHub-reviewed advisory GHSA-wmj8-9953-vff5 lists affected ranges: Go github.com/opencost/opencost >=0 <1.119.1)

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