ASTEVAL Allows Maliciously Crafted Format Strings to Lead 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

• CVE-2025-24359: 0.28% estimated exploitation activity in the next 30 days; percentile 20.32 (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.

Summary If an attacker can control the input to the asteval library, they can bypass asteval's restrictions and execute arbitrary Python code in the context of the application using the library. Details The vulnerability is rooted in how asteval performs handling of FormattedValue AST nodes. In particular, the onformattedvalue value uses the dangerous format method of the str class, as shown in the vulnerable code snippet below: The code above allows an attacker to manipulate the value of the string used in the dangerous call fmt.format(fstring=val). This vulnerability can be exploited to access protected attributes by intentionally triggering an AttributeError exception. The attacker can then catch the exception and use its obj attribute to gain arbitrary access to sensitive or protected object properties. PoC The following proof-of-concept (PoC) demonstrates how this vulnerability can be exploited to execute the whoami command on the host machine:

Published by the source

24 Jan 2025, 18:45 UTC

Last modified by the source

7 Jul 2026, 17:57 UTC

Source last checked

26 Oct 2026, 13:30 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-3wwr-3g9f-9gc7

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-3wwr-3g9f-9gc7

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# Patch Next advisory brief: CVE-2025-24359

Advisory: ASTEVAL Allows Maliciously Crafted Format Strings to Lead to Sandbox Escape
IDs: CVE-2025-24359, GHSA-3wwr-3g9f-9gc7
Record: https://patchnext.com/advisories/cve-2025-24359 (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-3wwr-3g9f-9gc7 (OSV record GHSA-3wwr-3g9f-9gc7 lists affected ranges: PyPI asteval >=0 <1.0.6 (fixed))
- Verified: https://github.com/advisories/GHSA-3wwr-3g9f-9gc7 (GitHub-reviewed advisory GHSA-3wwr-3g9f-9gc7 lists affected ranges: PyPI asteval >=0 <=1.0.5)

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