asteval Sandbox Escape: arbitrary native memory read/write via numpy ctypes in default asteval Interpreter

Exploitation

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

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary With its default configuration (numpy enabled, import disabled), asteval's Interpreter lets an attacker-controlled expression obtain a raw arbitrary process-memory read and write primitive, without using import, any dunder attribute, or eval/exec/getattr. Arbitrary in-process read/write is equivalent to arbitrary code execution and is a complete escape of the sandbox whose entire purpose is "untrusted string in, no arbitrary execution out." Any application that feeds untrusted input to asteval with numpy installed (the default) is affected. Details asteval's attribute filter (asteval/astutils.py: safegetattr) blocks every dunder name and blocks objects whose attribute value is identity-equal to one of the modules in UNSAFEMODULES = {io, os, sys, ctypes}. The ctypes module entry was added recently (commit 9d9d430) and correctly blocks ndarray.ctypes.ctypes. However, the module check is identity-only against the ctypes module. It does not cover ctypes type objects and their…

Published by the source

20 Aug 2026, 17:26 UTC

Last modified by the source

20 Aug 2026, 17:26 UTC

Source last checked

26 Oct 2026, 13:50 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-9w56-46f6-3qhx

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# Patch Next advisory brief: GHSA-9w56-46f6-3qhx

Advisory: asteval Sandbox Escape: arbitrary native memory read/write via numpy ctypes in default asteval Interpreter
IDs: GHSA-9w56-46f6-3qhx
Record: https://patchnext.com/advisories/ghsa-9w56-46f6-3qhx (revision 1, source checked 26 Oct 2026, 13:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: asteval 1.0.9. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI asteval: affected < 1.0.9; fixed in 1.0.9

## Suggested inspection (read-only)
- `python -m pip show asteval`: 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 asteval.
- 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-9w56-46f6-3qhx (GitHub-reviewed advisory GHSA-9w56-46f6-3qhx lists affected ranges: PyPI asteval >=0 <1.0.9)

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