Bug 1933737 (CVE-2020-27067)

Summary:	CVE-2020-27067 kernel: use after free due to a race condition may lead to local escalation of privilege
Product:	[Other] Security Response	Reporter:	Marian Rehak <mrehak>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED WONTFIX	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	acaringi, aclaudi, adscvr, airlied, alciregi, bdettelb, bhu, blc, bmasney, brdeoliv, bskeggs, chwhite, dhoward, dvlasenk, fhrbata, hdegoede, hkrzesin, jarodwilson, jeremy, jforbes, jlelli, jonathan, josef, jshortt, jstancek, jwboyer, kcarcia, kernel-maint, kernel-mgr, lgoncalv, linville, masami256, mchehab, mlangsdo, mleitner, nmurray, ptalbert, qzhao, rvrbovsk, steved, tomckay, walters, williams
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:	A flaw use-after-free in the Linux kernel l2tp subsystem was found in the way user initialize and use vpn connection over l2tp. A local user could use this flaw to escalate their privileges on the system. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2021-11-09 15:39:23 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:	1933738, 1940645, 1940647, 1940648
Bug Blocks:	1933739

Description Marian Rehak 2021-03-01 15:24:35 UTC

In the l2tp subsystem, there is a possible use after free due to a race condition, which could lead to local escalation of privilege with System execution privileges needed.

Reference:

https://source.android.com/security/bulletin/pixel/2020-12-01

Comment 1 Marian Rehak 2021-03-01 15:25:38 UTC

Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1933738]

Comment 2 Justin M. Forbes 2021-03-02 14:09:10 UTC

This was fixed for Fedora with the 4.13.6 stable kernel updates.

Comment 5 Alex 2021-03-18 19:07:56 UTC

Mitigation:

To mitigate this issue, prevent the module l2tp_core from being loaded. Please see https://access.redhat.com/solutions/41278 for information on how to blacklist a kernel module to prevent it from loading automatically.