CVE-2021-45100

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.

Weakness

The product transmits sensitive or security-critical data in cleartext in a communication channel that can be sniffed by unauthorized actors.

Affected Software

Extended Description

Many communication channels can be “sniffed” (monitored) by adversaries during data transmission. For example, in networking, packets can traverse many intermediary nodes from the source to the destination, whether across the internet, an internal network, the cloud, etc. Some actors might have privileged access to a network interface or any link along the channel, such as a router, but they might not be authorized to collect the underlying data. As a result, network traffic could be sniffed by adversaries, spilling security-critical data. Applicable communication channels are not limited to software products. Applicable channels include hardware-specific technologies such as internal hardware networks and external debug channels, supporting remote JTAG debugging. When mitigations are not applied to combat adversaries within the product’s threat model, this weakness significantly lowers the difficulty of exploitation by such adversaries. When full communications are recorded or logged, such as with a packet dump, an adversary could attempt to obtain the dump long after the transmission has occurred and try to “sniff” the cleartext from the recorded communications in the dump itself.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/102.html
• https://cwe.mitre.org/data/definitions/117.html
• https://cwe.mitre.org/data/definitions/383.html
• https://cwe.mitre.org/data/definitions/477.html
• https://cwe.mitre.org/data/definitions/65.html

References

• https://github.com/cifsd-team/ksmbd/issues/550
• https://github.com/cifsd-team/ksmbd/pull/551
• https://marc.info/?l=linux-kernel\u0026m=163961726017023\u0026w=2
• https://security.netapp.com/advisory/ntap-20220107-0001/
• https://github.com/cifsd-team/ksmbd/issues/550
• https://github.com/cifsd-team/ksmbd/pull/551
• https://marc.info/?l=linux-kernel\u0026m=163961726017023\u0026w=2
• https://security.netapp.com/advisory/ntap-20220107-0001/