Bug 2293948 (CVE-2023-6507)

Summary:	CVE-2023-6507 python: Improper privileges drop on subprocess module
Product:	[Other] Security Response	Reporter:	Marco Benatto <mbenatto>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	agarcial, aoconnor, aprice, asegurap, bdettelb, caswilli, dfreiber, drow, fjansen, hkataria, jburrell, jmitchel, jsamir, jsherril, jtanner, kaycoth, kholdawa, kshier, lbalhar, mpierce, orabin, sthirugn, vkrizan, vkumar, xiaoxwan, zzhou
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	python 3.12.1	Doc Type:	If docs needed, set a value
Doc Text:	A flaw was found in Python's subprocess module. When creating a new subprocess, the developer may specify a list of extra groups through the 'extra_groups=` parameter. When this optional parameter is informed with an empty list, the module fails to properly clean the associated groups from the new sub-process's parent before executing the new sub-process. If the parent process has high privileges, the sub-process created may have unnecessarily high privileges, leading to possible confidentiality and integrity issues when properly exploited.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	2293949

Description Marco Benatto 2024-06-24 15:17:04 UTC

An issue was found in CPython 3.12.0 `subprocess` module on POSIX platforms. The issue was fixed in CPython 3.12.1 and does not affect other stable releases.

When using the `extra_groups=` parameter with an empty list as a value (ie `extra_groups=[]`) the logic regressed to not call `setgroups(0, NULL)` before calling `exec()`, thus not dropping the original processes' groups before starting the new process. There is no issue when the parameter isn't used or when any value is used besides an empty list.

This issue only impacts CPython processes run with sufficient privilege to make the `setgroups` system call (typically `root`).

References:
https://mail.python.org/archives/list/security-announce@python.org/thread/AUL7QFHBLILGISS7U63B47AYSSGJJQZD/
https://github.com/python/cpython/issues/112334

Upstream patches:
https://github.com/python/cpython/commit/10e9bb13b8dcaa414645b9bd10718d8f7179e82b
https://github.com/python/cpython/commit/85bbfa8a4bbdbb61a3a84fbd7cb29a4096ab8a06
https://github.com/python/cpython/commit/9fe7655c6ce0b8e9adc229daf681b6d30e6b1610