Bug 1771690 (CVE-2019-18684)

Summary:	CVE-2019-18684 sudo: privilege escalation via write access to file descriptor 3 of the sudo process
Product:	[Other] Security Response	Reporter:	msiddiqu
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	dapospis, dkopecek, kzak, mattdm, rsroka, tjaros, tosykora, yozone
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2019-11-18 13:26:16 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	1771692

Description msiddiqu 2019-11-12 19:18:46 UTC

Sudo through 1.8.29 allows local users to escalate to root if they have writeaccess to file descriptor 3 of the sudo process. This occurs because of a racecondition between determining a uid, and the setresuid and openat system calls.The attacker can write "ALL ALL=(ALL) NOPASSWD:ALL" to /proc/#####/fd/3 at atime when Sudo is prompting for a password.

References: 
 
https://gist.github.com/oxagast/51171aa161074188a11d96cbef884bbd

Comment 1 Riccardo Schirone 2019-11-18 13:26:16 UTC

Closing this flaw bug as NOTABUG as the CVE has been DISPUTED.

To be able to access /proc/<sudo-pid>/fd/<sudoers-fd>, an attacker should already be able to access it.