Bug 2035345 (CVE-2021-45100) - CVE-2021-45100 kernel: ksmbd server communicates in cleartext even though encryption has been enabled due to a violation of the SMB protocol specification
Summary: CVE-2021-45100 kernel: ksmbd server communicates in cleartext even though enc...
Keywords:
Status: CLOSED NOTABUG
Alias: CVE-2021-45100
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
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Depends On: 2035346
Blocks: Embargoed2035347
TreeView+ depends on / blocked
 
Reported: 2021-12-23 17:12 UTC by Guilherme de Almeida Suckevicz
Modified: 2022-01-26 19:54 UTC (History)
47 users (show)

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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.
Clone Of:
Environment:
Last Closed: 2022-01-07 13:51:09 UTC

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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
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