CVE-2026-55244
ASTEVAL: Sandbox Escape via BaseException Subclasses
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
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.
Public exploit
A reference of the record is tagged as an exploit or proof of concept: anyone can try it against an unpatched system. CISA's SSVC rates its exploitation: a proof of concept is public.
- https://github.com/lmfit/asteval/security/advisories/GHSA-89v8-rhwq-hf77 (opens in a new tab)x_refsource_CONFIRMexploit
Timeline
ID reserved
By GitHub_M
- 3 months later
· 3 months later
Published
- 2 days later
· 2 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | Medium5.0 | CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H |
| NVDNVD · Deferred | 3.1 | Medium5.0 | CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.18% · top 93% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.0.
Weakness
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- PyPIastevalGHSA-89v8-rhwq-hf77 (opens in a new tab)
References (5)
- https://github.com/lmfit/asteval/security/advisories/GHSA-89v8-rhwq-hf77 (opens in a new tab)x_refsource_CONFIRMexploit
- https://github.com/lmfit/asteval/pull/153 (opens in a new tab)x_refsource_MISC
- https://github.com/lmfit/asteval/commit/9c625b3674f8d05f206708bb85afca17a87694a4 (opens in a new tab)x_refsource_MISC
- https://github.com/lmfit/asteval/commit/c49c99a67acb63eb7410231932250bd820380e45 (opens in a new tab)x_refsource_MISC
- https://github.com/lmfit/asteval/releases/tag/1.0.9 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-89v8-rhwq-hf77 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-55244)Record last updated .