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CVE-2021-22538

Vulnerability in github.com/google/exposure-notifications-verification-server (CVE-2021-22538)

Summary

Vulnerability in github.com/google/exposure-notifications-verification-server (CVE-2021-22538). Successful exploitation can lead to full system takeover. Exploitable via UserWrite. Mitigation: upgrade to 0.24.0 or later.

Original description

The description as published by the source.

Impact

Using a carefully crafted request or malicious proxy, a user with UserWrite permissions could create another user with higher privileges than their own due to insufficient checks on the allowed set of permissions. The event would be captured in the Event Log.

Patches

The issue has been fixed in 0.24.0 and 0.23.1.

Workarounds

For users who are unable to upgrade, we recommend auditing users who have UserWrite permissions and regularly reviewing the Event Log for malicious activity.

Kudos

Thank you to Michael Mazzolini (Ethical Hacker at WHO) for finding and disclosing this vulnerability.

Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV

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-2021-22538 has been found in github.com/google/exposure-notifications-verification-server.
Attackers can target a specific entry point like UserWrite over the network to misuse the product.
Successful exploitation can lead to full system takeover.
What to do: upgrade github.com/google/exposure-notifications-verification-server to 0.24.0 or later.
If unsure, ask your IT team or search "github.com/google/exposure-notifications-verification-server CVE-2021-22538" on the vendor's site.

CVE-2021-22538 (github.com/google/exposure-notifications-verification-server) — CWE-276
Attack vector: remote (network-reachable) / no user interaction
Attack surface: UserWrite
Patched: 0.24.0 — apply immediately
Workaround: For users who are unable to upgrade, we recommend auditing users who have UserWrite permissions and regularly reviewing the Event Log for malicious activity.
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-276) exists in github.com/google/exposure-notifications-verification-server. Attackers reach the vulnerable code path via UserWrite.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/google/exposure-notifications-verification-server. Attack surface: UserWrite.

🔥 Severity

Severity: ?. Successful exploitation can lead to full system takeover.

🔧 How to fix

Update to 0.24.0.

🛡️ Workaround

Workaround: For users who are unable to upgrade, we recommend auditing users who have UserWrite permissions and regularly reviewing the Event Log for malicious activity.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'github.com/google/exposure-notifications-verification-server' . 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/google/exposure-notifications-verification-server' . | 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/google/exposure-notifications-verification-server 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 
    For users who are unable to upgrade, we recommend auditing users who have `UserWrite` permissions and regularly reviewing the Event Log for malicious activity.

    パッチが適用されるまでの応急処置として、For users who are unable to upgrade, we recommend auditing users who have UserWrite permissions and regularly reviewing the Event Log for malicious activity. 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/google/exposure-notifications-verification-server to 0.24.0

    ステージング環境で 0.24.0 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/google/exposure-notifications-verification-server
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.23.1"}]}]

References

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