CVE-2026-44300Public exploitNetwork attack vector

Unauthenticated credential overwrite via serviceKey file write

Published Sep 15, 2026 · Updated Sep 15, 2026

Improper input validation in OpenCost before 1.121.0 allows remote attackers to overwrite its GCP service-account key via POST /serviceKey. The unauthenticated AddServiceKey handler reads the key form value and passes its bytes directly to os.WriteFile at the fixed CONFIG_PATH/key.json path without validating the credential. Reachability to the HTTP service is sufficient; replacing that file can interrupt GCP cost collection or make OpenCost use attacker-selected credentials.

CVSS severity8.8
High
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in OpenCost before 1.121.0 allows remote attackers to overwrite its GCP service-account key via POST /serviceKey. The unauthenticated AddServiceKey handler reads the key form value and passes its bytes directly to os.WriteFile at the fixed CONFIG_PATH/key.json path without validating the credential. Reachability to the HTTP service is sufficient; replacing that file can interrupt GCP cost collection or make OpenCost use attacker-selected credentials.

The record

CVE
CVE-2026-44300
Published
Sep 15, 2026
Updated
Sep 15, 2026
Vendor
OpenCost
Product
OpenCost
Classifications
CWE-309, CWE-20, T1565.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 15, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.121.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenCost · OpenCostversion=< 1.121.0

Published CVSS scores

8.8GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-309Use of Password System for Primary Authentication
CWE-20Improper Input Validation
T1565.001Stored Data Manipulation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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