← Back
CVE-2026-59876
medium
CVSS 4.8
Vulnerability in protobufjs (CVE-2026-59876)
Summary
vulnerability in protobufjs (CVE-2026-59876). Risk of unauthorized operations or information disclosure. Exploitable via ``__proto__``. Mitigation: upgrade to `8.6.5` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2026-59876** has been found in protobufjs.
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: 4.8/10.
What to do: upgrade protobufjs to **8.6.5** or later.
If unsure, ask your IT team or search "protobufjs CVE-2026-59876" on the vendor's site.
CVE-2026-59876 (protobufjs) — CWE-1321 / CVSS v3 4.8
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: `__proto__` / `fromObject` / `Object.prototype`
Patched: `8.6.5` — 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 protobufjs. Attackers reach the vulnerable code path via ``__proto__`` without authentication.
📍 Affected scope
protobufjs — . Attack surface: `__proto__` / `fromObject` / `Object.prototype`.
🔥 Severity
Severity: Medium (CVSS 4.8/10). Risk of unauthorized operations or information disclosure
🔧 How to fix
Update to **8.6.5**.
🛡️ 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 'protobufjs' .` against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response Actions (7 steps)
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'protobufjs' . | 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 `protobufjs` を grep し、稼働しているサービス・バージョンを把握する。
-
6Apply patch patch
Upgrade protobufjs to 8.6.5ステージング環境で 8.6.5 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と、Step 3 で見つけた異常検知の続報チェックを含めること。
-
7Post-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 Step 3 と同じログクエリでアラート再発が無いか継続監視。
Affected packages
npm
protobufjs
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"8.6.5"}]}]
References
- web https://github.com/protobufjs/protobuf.js/commit/9f97fe413072d3beb52c74e62d88ea8adc9444d8
- web https://github.com/protobufjs/protobuf.js/pull/2335
- web https://github.com/protobufjs/protobuf.js/releases/tag/protobufjs-v8.6.5
- web https://github.com/protobufjs/protobuf.js/security/advisories/GHSA-jfj6-75fj-8934
- web https://nvd.nist.gov/vuln/detail/CVE-2026-59876
- web https://github.com/advisories/GHSA-jfj6-75fj-8934