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CVE-2026-73647 medium CVSS 5.6

Vulnerability in quasar (CVE-2026-73647)

Summary

Vulnerability in quasar (CVE-2026-73647). Risk of unauthorized operations or information disclosure. Exploitable via __proto__. Mitigation: upgrade to 2.22.0 or later.

Original description

The description as published by the source.

Summary

quasar@2.20.1, the latest published version at the time of testing, appears to be vulnerable to prototype pollution through the public extend() utility exported from the package root.

When extend(true, target, source) is used for a deep merge, attacker-controlled object keys are recursively copied into the target object without blocking prototype-pollution primitives such as __proto__, constructor, or prototype.

This can allow attacker-controlled properties to be written to Object.prototype.

Details

Affected source:

src/utils/extend/extend.js

Distributed files include:

dist/quasar.server.prod.js
dist/quasar.server.prod.cjs
dist/quasar.client.js

The package root publicly exports extend. During deep merge, source object keys are recursively assigned into the target object. If the source object contains an own __proto__ property, the merge can descend into the prototype object and assign attacker-controlled properties onto Object.prototype.

PoC

rm -rf /tmp/quasar-extend-pp-poc
mkdir /tmp/quasar-extend-pp-poc
cd /tmp/quasar-extend-pp-poc

npm init -y >/dev/null
npm install quasar@2.20.1 vue@3.5.31 >/dev/null

cat > hack.mjs <<'JS'
import { extend } from 'quasar';

delete Object.prototype.polluted;

extend(true, {}, {
  ['__proto__']: {
    polluted: 'yes'
  }
});

console.log(({}).polluted);

delete Object.prototype.polluted;
JS

node ./hack.mjs

Observed output:

yes

Expected outp…

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-2026-73647 has been found in quasar.
Attackers can target a specific entry point like __proto__ over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.6/10.
What to do: upgrade quasar to 2.22.0 or later.
If unsure, ask your IT team or search "quasar CVE-2026-73647" on the vendor's site.

CVE-2026-73647 (quasar) — CWE-1321 / CVSS v3 5.6
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: __proto__ / constructor / prototype / Object.prototype
Patched: 2.22.0 — apply immediately
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-1321) exists in quasar. Attackers reach the vulnerable code path via __proto__ without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of quasar. Attack surface: __proto__ / constructor / prototype / Object.prototype.

🔥 Severity

Severity: Medium (CVSS 5.6/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 2.22.0.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'quasar' . 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 'quasar' . | 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 quasar 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 patch patch 
    Upgrade quasar to 2.22.0

    ステージング環境で 2.22.0 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。

  3. 3
    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

npm quasar
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.22.0"}]}]

References

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