ASTEVAL Allows Malicious Tampering of Exposed AST Nodes Leads to Sandbox Escape

Exploitation

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

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary If an attacker can control the input to the asteval library, they can bypass its safety restrictions and execute arbitrary Python code within the application's context. Details The vulnerability is rooted in how asteval performs attribute access verification. In particular, the onattribute node handler prevents access to attributes that are either present in the UNSAFEATTRS list or are formed by names starting and ending with , as shown in the code snippet below: While this check is intended to block access to sensitive Python dunder methods (such as getattribute), the flaw arises because instances of the Procedure class expose their AST (stored in the body attribute) without proper protection: Since the body attribute is not protected by a naming convention that would restrict its modification, an attacker can modify the AST of a Procedure during runtime to leverage unintended behaviour. The exploit works as follows: 1. The Time of Check, Time of Use (TOCTOU) Gadget: In the…

Published by the source

23 Jan 2025, 22:33 UTC

Last modified by the source

23 Jan 2025, 22:45 UTC

Source last checked

26 Oct 2026, 13:30 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-vp47-9734-prjw

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-vp47-9734-prjw

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# Patch Next advisory brief: GHSA-vp47-9734-prjw

Advisory: ASTEVAL Allows Malicious Tampering of Exposed AST Nodes Leads to Sandbox Escape
IDs: GHSA-vp47-9734-prjw
Record: https://patchnext.com/advisories/ghsa-vp47-9734-prjw (revision 2, source checked 26 Oct 2026, 13:30 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: asteval 1.0.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI asteval: affected <= 1.0.5; fixed in 1.0.6

## 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://osv.dev/vulnerability/GHSA-vp47-9734-prjw (OSV record GHSA-vp47-9734-prjw lists affected ranges: PyPI asteval >=0 <1.0.6 (fixed))
- Verified: https://github.com/advisories/GHSA-vp47-9734-prjw (GitHub-reviewed advisory GHSA-vp47-9734-prjw lists affected ranges: PyPI asteval >=0 <=1.0.5)

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