Sandbox escape in smolagents Local Python execution environment via dunder attributes

published 2025-09-03 last yr. modified 2026-09-26 last mo. also EUVD-2025-26607

cvss: 7.6; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 24%
public exploits: 0; none known

Incomplete validation of dunder attributes allows an attacker to escape from the Local Python execution environment sandbox, enforced by smolagents. The attack requires a Prompt Injection in order to trick the agent to create malicious code.

Patch / fix

links 1

github.com/huggingface/smolagents#1551 pull request

Is CVE-2025-9959 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: last yr. (2025-09-03)

Exploit prediction

0.31% chance of exploitation in the next 30 days, higher than 24% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.6	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:L

Classification

Weakness

CWE-94 Improper Control of Generation of Code

References

github.com /huggingface/smolagents/pull/1551
patch
research.jfrog.com /vulnerabilities/smolagents-local-python-sandbox-escape-jfsa-2025-001434277/
third-party-advisory

Sources

CVE List CVE-2025-9959
NVD CVE-2025-9959

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.