Bug 2035345 (CVE-2021-45100)

Summary:	CVE-2021-45100 kernel: ksmbd server communicates in cleartext even though encryption has been enabled due to a violation of the SMB protocol specification
Product:	[Other] Security Response	Reporter:	Guilherme de Almeida Suckevicz <gsuckevi>
Component:	vulnerability	Assignee:	Red Hat Product Security <security-response-team>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	acaringi, adscvr, airlied, alciregi, bdettelb, bhu, brdeoliv, bskeggs, chwhite, crwood, dhoward, dvlasenk, fhrbata, fpacheco, hdegoede, hkrzesin, jarod, jarodwilson, jburrell, jeremy, jfaracco, jforbes, jglisse, jlelli, jonathan, josef, jshortt, jstancek, jwboyer, kcarcia, kernel-maint, kernel-mgr, lgoncalv, linville, lzampier, masami256, mchehab, nmurray, ptalbert, qzhao, rvrbovsk, scweaver, sgrubb, steved, vkumar, 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:	An unexpected, non-encrypted communication flaw in the Linux kernel's ksmbd (Samba 3 protocol implementation) subsystem was found in the way when user set flag SMB2_GLOBAL_CAP_ENCRYPTION using the SMB 3.1.1 protocol. If during connection flag SMB2_GLOBAL_CAP_ENCRYPTION being used by remote user, then for some conditions the connection becomes unencrypted.	Story Points:	---
Clone Of:		Environment:
Last Closed:	2022-01-07 13:51:09 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:	2035346
Bug Blocks:	2035347

Description Guilherme de Almeida Suckevicz 2021-12-23 17:12:25 UTC

The ksmbd server through 3.4.2, as used in the Linux kernel through 5.15.8, sometimes communicates in cleartext even though encryption has been enabled. This occurs because it sets the SMB2_GLOBAL_CAP_ENCRYPTION flag when using the SMB 3.1.1 protocol, which is a violation of the SMB protocol specification. When Windows 10 detects this protocol violation, it disables encryption.

Reference:
https://github.com/cifsd-team/ksmbd/issues/550

Upstream patches:
https://github.com/cifsd-team/ksmbd/pull/551
https://marc.info/?l=linux-kernel&m=163961726017023&w=2

Comment 1 Guilherme de Almeida Suckevicz 2021-12-23 17:12:59 UTC

Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 2035346]

Comment 2 Justin M. Forbes 2021-12-23 20:32:53 UTC

# CONFIG_SMB_SERVER is not set in the 5.15 kernel series for Fedora.

Comment 3 Product Security DevOps Team 2022-01-07 13:51:05 UTC

This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2021-45100