RestrictedPython: Sandbox escape via string.Formatter field resolution

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-76825
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-16 15:17:46 UTC
Updated2026-09-16 19:17:34 UTC
DescriptionRestrictedPython is a tool that helps define a subset of the Python language for accepting program input in a trusted environment. Prior to 8.4, RestrictedPython could allow a sandbox escape when a custom import policy or globals exposed the standard library string module, the string.Formatter class, a Formatter instance, or a Formatter subclass to restricted code. The string.Formatter methods format, get_field, get_value, and vformat performed attribute and item traversal internally without passing through RestrictedPython's safer_getattr protections. Restricted code could use those live object references to reach function globals, builtins, file access, or code execution primitives, affecting confidentiality, integrity, and availability in the host environment. This issue is fixed in version 8.4.

Risk And Classification

Primary CVSS: v3.1 8.4 HIGH from [email protected]

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

Problem Types: CWE-200 | CWE-470 | CWE-680 | CWE-693 | CWE-200 CWE-200: Exposure of Sensitive Information to an Unauthorized Actor | CWE-470 CWE-470: Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') | CWE-680 CWE-680: Integer Overflow to Buffer Overflow | CWE-693 CWE-693: Protection Mechanism Failure

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8.4HIGHCVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:H
3.1CNADECLARED8.4HIGHCVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
High
User Interaction
Required
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Zopefoundation RestrictedPython affected < 8.4 Not specified

References

ReferenceSourceLinkTags
github.com/zopefoundation/RestrictedPython/commit/3b47440070b91f8807c2b2... [email protected] github.com
github.com/zopefoundation/RestrictedPython/releases/tag/8.4 [email protected] github.com
github.com/zopefoundation/RestrictedPython/security/advisories/GHSA-hp3v... [email protected] github.com
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