ASTEVAL: Sandbox Escape via BaseException Subclasses

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-55244
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-14 20:16:47 UTC
Updated2026-09-30 17:51:56 UTC
DescriptionASTEVAL is an evaluator of Python expressions and statements. Prior to 1.0.9, FROM_PY in asteval/astutils.py exposes BaseException, SystemExit, KeyboardInterrupt, and GeneratorExit to expressions evaluated by asteval.Interpreter.eval(), while run() and eval() in asteval/asteval.py catch Exception rather than these non-Exception BaseException subclasses. When an attacker-controlled expression raises one of these classes, on_raise() passes the class to raise_exception(), and the resulting exception bypasses the interpreter's safety handlers and propagates into the calling application. A consuming service that evaluates untrusted expressions can therefore be terminated or have signal and cleanup handling disrupted, causing denial of service. The separately documented read-only open() capability is not part of this vulnerability. This issue is fixed in version 1.0.9.

Risk And Classification

Primary CVSS: v3.1 5 MEDIUM from [email protected]

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

EPSS: 0.001770000 probability, percentile 0.068190000 (date 2026-10-16)

Problem Types: CWE-248 | CWE-248 CWE-248: Uncaught Exception

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
3.1CNADECLARED5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Lmfit Asteval affected < 1.0.9 Not specified

References

ReferenceSourceLinkTags
github.com/lmfit/asteval/commit/c49c99a67acb63eb7410231932250bd820380e45 [email protected] github.com
github.com/lmfit/asteval/releases/tag/1.0.9 [email protected] github.com
github.com/lmfit/asteval/pull/153 [email protected] github.com
github.com/lmfit/asteval/security/advisories/GHSA-89v8-rhwq-hf77 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/lmfit/asteval/commit/9c625b3674f8d05f206708bb85afca17a87694a4 [email protected] github.com
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