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CVE-2026-55830 high CVSS 8.3

Vulnerability in RestrictedPython (CVE-2026-55830)

Summary

Vulnerability in RestrictedPython (CVE-2026-55830). Confidential information can be exposed externally. Exploitable via _write_. Mitigation: upgrade to 8.3 or later.

Original description

The description as published by the source.

Impact

RestrictedPython rewrites sensitive operations to go through guard hooks. Attribute access becomes _getattr_(obj, name), item access becomes _getitem_(obj, key), writes go through _write_, and print goes through _print_. The embedding application supplies these hooks to enforce its policy.

Argument-name validation rejects these protected names for regular arguments, *args, **kwargs, and keyword-only arguments, but it misses positional-only arguments (the ones before /). So a function like:

def f(_getattr_=evil, /):
    return o.x

makes _getattr_ a local that shadows the policy hook, and the rewritten access calls evil instead. The same works for _getitem_, _write_, and _print_. Shadowing _print_ can also be used to capture the internal _getattr_ hook that RestrictedPython passes in.

The result is that sandboxed code can bypass the access policy the embedding application relies on. In applications that also handle sandbox-controlled objects unsafely (for example serializing them with pickle), this primitive can be chained further, up to remote code execution. That part depends on the embedding application, but the underlying guard bypass is in RestrictedPython.

Proof of concept

On an unpatched RestrictedPython this prints shadowed and an empty calls list, meaning the policy _getattr_ never ran. With the fix, compile_restricted rejects the code.

from RestrictedPython import compile_restricted
fro…

Source: NIST National Vulnerability Database 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-2026-55830 has been found in RestrictedPython.
Attackers can target a specific entry point like _write_ over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 8.3/10.
What to do: upgrade RestrictedPython to 8.3 or later.
If unsure, ask your IT team or search "RestrictedPython CVE-2026-55830" on the vendor's site.

CVE-2026-55830 (RestrictedPython) — CWE-184 / CVSS v3 8.3
Attack vector: remote (network-reachable)
Attack surface: _write_ / _print_ / _getattr_ / evil
Patched: 8.3 — apply immediately
Workaround: None other than upgrading.
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-184) exists in RestrictedPython. Attackers reach the vulnerable code path via _write_.

📍 Affected scope

Check the vendor advisory for the affected versions of RestrictedPython. Attack surface: _write_ / _print_ / _getattr_ / evil.

🔥 Severity

Severity: High (CVSS 8.3/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 8.3.

🛡️ Workaround

Workaround: None other than upgrading.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'RestrictedPython' . 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 'RestrictedPython' . | 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 RestrictedPython 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 
    None other than upgrading.

    パッチが適用されるまでの応急処置として、None other than upgrading. 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 RestrictedPython to 8.3

    ステージング環境で 8.3 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

pip RestrictedPython
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"8.3"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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