Is CVE-2026-55244 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-55244 being exploited in the wild.

How severe is CVE-2026-55244?

Medium severity, with a CVSS score of 5, published 14 September 2026.

Which products and versions are affected?

asteval (PyPI) < 1.0.9, ECOSYSTEM:introduced=0,fixed=1.0.9.

Is there a fix for CVE-2026-55244?

Yes. asteval (PyPI): upgrade to 1.0.9 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-55244 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-55244?

Check whether you run asteval (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-55244: asteval Interpreter sandbox escape via BaseException subclasses

Q: Which products and versions are affected?

asteval (PyPI) < 1.0.9, ECOSYSTEM:introduced=0,fixed=1.0.9.

Q: Is there a fix for CVE-2026-55244?

Yes. asteval (PyPI): upgrade to 1.0.9 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Q: How is CVE-2026-55244 attacked?

It is attacked over the network, in a software library.

Q: Am I affected by CVE-2026-55244?

Check whether you run asteval (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-55244 · Severity: medium · CVSS 5 · Published 2026-09-14

asteval is a Python library that safely evaluates mathematical and Python expressions within a sandboxed interpreter. An attacker who can supply untrusted expressions to the interpreter can raise uncontrolled exceptions (SystemExit, KeyboardInterrupt, GeneratorExit, or BaseException) that bypass the sandbox's exception handling and propagate to the calling application, causing process termination or disruption of signal handlers and cleanup code. This results in denial of service.

Technologies: asteval (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-55244 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-55244 being exploited in the wild.
How severe is CVE-2026-55244?: Medium severity, with a CVSS score of 5, published 14 September 2026.
Which products and versions are affected?: asteval (PyPI) < 1.0.9, ECOSYSTEM:introduced=0,fixed=1.0.9.
Is there a fix for CVE-2026-55244?: Yes. asteval (PyPI): upgrade to 1.0.9 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-55244 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-55244?: Check whether you run asteval (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

asteval (PyPI): upgrade to 1.0.9 or later
```
pip install "asteval>=1.0.9"
```

Technical details

The vulnerability exists in asteval's exception hierarchy handling. The FROM_PY tuple in astutils.py (lines 89–108) exposes dangerous exception classes including BaseException, SystemExit, KeyboardInterrupt, and GeneratorExit to sandbox users. When a user expression raises one of these exceptions, they bypass the except Exception: guards in run() (line 322) and eval() (line 370) because these non-Exception subclasses of BaseException are not caught by except Exception:. The exception then propagates uncontrolled to the calling application. The attack is network-reachable if the application accepts user-supplied expressions, requires no authentication or user interaction, and affects availability through process termination or handler disruption. The vulnerability exists in all versions up to and including 1.0.6. A patch is available in version 1.0.9, which removes the dangerous classes from FROM_PY.

Affected products

lmfit asteval < 1.0.9

Identifiers

CVE-2026-55244
GHSA-89v8-rhwq-hf77
PYSEC-2026-3807

Timeline

2026-06-09: disclosed: Vulnerability discovered during code review
2026-06-11: advisory: GitHub Security Advisory published
2026-08-20: patched: Fix released in version 1.0.9

References

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