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CVE-2026-23998 high CVSS 7.5

Vulnerability in github.com/fleetdm/fleet/v4 (CVE-2026-23998)

Summary

Vulnerability in github.com/fleetdm/fleet/v4 (CVE-2026-23998). Confidential information can be exposed externally. Mitigation: upgrade to 4.81.0 or later.

Original description

The description as published by the source.

Summary

A vulnerability in Fleet’s Windows MDM management endpoint could allow requests to be processed without proper client certificate validation. In certain circumstances, this could allow an attacker to impersonate an enrolled Windows device and retrieve sensitive configuration data.

Impact

Fleet’s Windows MDM management endpoint relies on mutual TLS (mTLS) client certificates to authenticate enrolled devices. In affected versions, requests that did not present a client certificate could be incorrectly treated as trusted.

As a result, an attacker with prior knowledge of a valid enrolled device identifier could potentially impersonate that device and receive configuration payloads intended for it. These payloads may contain sensitive information such as Wi-Fi or VPN configuration data, certificates, or other secrets delivered through MDM profiles.

This issue does not allow enrollment of new devices, administrative access to Fleet, or compromise of the Fleet control plane. Impact is limited to the targeted Windows device.

Workarounds

If an immediate upgrade is not possible, affected Fleet users should temporarily disable Windows MDM.

For more information

If you have any questions or comments about this advisory:

Email us at security@fleetdm.com
Join #fleet in osquery Slack

Credits

We thank @secfox-ai for responsibly reporting t…

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-23998 has been found in github.com/fleetdm/fleet/v4.
Confidential information can be exposed externally. CVSS score: 7.5/10.
What to do: upgrade github.com/fleetdm/fleet/v4 to 4.81.0 or later.
If unsure, ask your IT team or search "github.com/fleetdm/fleet/v4 CVE-2026-23998" on the vendor's site.

CVE-2026-23998 (github.com/fleetdm/fleet/v4) — CWE-295 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 4.81.0 — apply immediately
Workaround: If an immediate upgrade is not possible, affected Fleet users should temporarily disable Windows MDM.
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-295) exists in github.com/fleetdm/fleet/v4.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/fleetdm/fleet/v4.

🔥 Severity

Severity: High (CVSS 7.5/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 4.81.0.

🛡️ Workaround

Workaround: If an immediate upgrade is not possible, affected Fleet users should temporarily disable Windows MDM.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'github.com/fleetdm/fleet/v4' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'github.com/fleetdm/fleet/v4' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で github.com/fleetdm/fleet/v4 を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply temporary workaround mitigate 
    If an immediate upgrade is not possible, affected Fleet users should temporarily disable Windows MDM.

    パッチが適用されるまでの応急処置として、If an immediate upgrade is not possible, affected Fleet users should temporarily disable Windows MDM. を実施。回避策の副作用 (機能低下) を確認した上で。

  3. 3
    Apply patch patch 
    Upgrade github.com/fleetdm/fleet/v4 to 4.81.0

    ステージング環境で 4.81.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  4. 4
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

go github.com/fleetdm/fleet/v4
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"4.81.0"}]}]

References

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