# CVE-2026-55244

## Summary

- **CVE ID:** CVE-2026-55244
- **Severity:** MEDIUM
- **CVSS Score:** 5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H)
- **CWE:** CWE-248
- **Published:** Sep 14, 2026
- **Last Modified:** Sep 16, 2026

## Description

ASTEVAL 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.

## Affected Products

- lmfit — asteval (< 1.0.9)

## References

- [CNA](https://github.com/lmfit/asteval/security/advisories/GHSA-89v8-rhwq-hf77)
- [CNA](https://github.com/lmfit/asteval/pull/153)
- [CNA](https://github.com/lmfit/asteval/commit/9c625b3674f8d05f206708bb85afca17a87694a4)
- [CNA](https://github.com/lmfit/asteval/commit/c49c99a67acb63eb7410231932250bd820380e45)
- [CNA](https://github.com/lmfit/asteval/releases/tag/1.0.9)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.19%
- **EPSS Percentile:** 9.0

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-18._