CVE-2026-55830
Sandbox bypass in RestrictedPython via positional-only argument shadowing
Is CVE-2026-55830 being exploited?
Not confirmed. CVE-2026-55830 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.40% probability of exploitation in the next 30 days.
How severe is CVE-2026-55830?
CVE-2026-55830 is rated High with a CVSS score of 8.3. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-55830?
Yes. A fix has been recorded for CVE-2026-55830. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-55830 affect?
CVE-2026-55830 affects RestrictedPython < 8.3, Applications embedding RestrictedPython, Any sandboxed Python environment using this library. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-55830?
Upgrade to RestrictedPython v8.3 immediately
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Bypass embedding application's access policy: attackers can shadow guard hooks (e.g., __getattr__, _write_, _print_) to access protected attributes/functions and exfiltrate data or perform unauthorized actions.
Immediate action required
- affected< 8.3
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.