RestrictedPython vulnerable to sandbox escape via string.Formatter field resolution

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.4 · CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:H

EPSS

• CVE-2026-76825: 0.62% estimated exploitation activity in the next 30 days; percentile 49.99 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact RestrictedPython could allow a sandbox escape when a policy exposes the standard library string module, or otherwise exposes string.Formatter, to restricted code. string.Formatter field resolution methods such as getfield can perform attribute and item traversal internally and return live object references. This can bypass RestrictedPython's normal attribute guards and may allow access to sensitive objects such as function globals, builtins, file access, or code execution primitives. Users are impacted if they run untrusted code with RestrictedPython and expose string.Formatter, directly or indirectly, for example through a custom import policy or globals. Patches The problem has been patched by blocking access to string.Formatter and unsafe string.Formatter traversal methods in safergetattr. Users should upgrade to the patched release once available. Affected and patched version numbers should be filled in when the release is published. Workarounds Do not expose the standard…

Published by the source

17 Sep 2026, 16:30 UTC

Last modified by the source

1 Oct 2026, 17:55 UTC

Source last checked

26 Oct 2026, 13:54 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-hp3v-5vw7-fx9w

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-hp3v-5vw7-fx9w

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-hp3v-5vw7-fx9w

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# Patch Next advisory brief: CVE-2026-76825

Advisory: RestrictedPython vulnerable to sandbox escape via string.Formatter field resolution
IDs: CVE-2026-76825, GHSA-hp3v-5vw7-fx9w
Record: https://patchnext.com/advisories/cve-2026-76825 (revision 3, source checked 26 Oct 2026, 13:54 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: restrictedpython 8.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI restrictedpython: affected < 8.4; fixed in 8.4

## Suggested inspection (read-only)
- `python -m pip show restrictedpython`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on restrictedpython.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-hp3v-5vw7-fx9w (GitHub-reviewed advisory GHSA-hp3v-5vw7-fx9w lists affected ranges: PyPI restrictedpython >=0 <8.4)
- Verified: https://osv.dev/vulnerability/GHSA-hp3v-5vw7-fx9w (OSV record GHSA-hp3v-5vw7-fx9w lists affected ranges: PyPI restrictedpython >=0 <8.4 (fixed))

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