CVE-2020-28374

Published: 12 January 2021

In drivers/target/target_core_xcopy.c in the Linux kernel before 5.10.7, insufficient identifier checking in the LIO SCSI target code can be used by remote attackers to read or write files via directory traversal in an XCOPY request, aka CID-2896c93811e3. For example, an attack can occur over a network if the attacker has access to one iSCSI LUN. The attacker gains control over file access because I/O operations are proxied via an attacker-selected backstore.

From the Ubuntu Security Team

It was discovered that the LIO SCSI target implementation in the Linux kernel performed insufficient identifier checking in certain XCOPY requests. An attacker with access to at least one LUN in a multiple backstore environment could use this to expose sensitive information or modify data.

Notes

MITIGATION
XCOPY support is enabled by default, but can be disabled via:
echo 0 > /sys/kernel/config/target/core/<backstore>/<name>/attrib/emulate_3pc
or
targetcli /backstores/<backstore>/<name> set attribute emulate_3pc=0
.
This workaround does *not* affect XCOPY requests sent to tcmu-runner
based backstores.

Mitigation

XCOPY support is enabled by default, but can be disabled via:
  echo 0 > /sys/kernel/config/target/core/<backstore>/<name>/attrib/emulate_3pc
or
  targetcli /backstores/<backstore>/<name> set attribute emulate_3pc=0
.
This workaround does *not* affect XCOPY requests sent to tcmu-runner
based backstores.

Status

Severity score breakdown

References

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-28374
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2896c93811e39d63a4d9b63ccf12a8fbc226e5e4
• https://github.com/open-iscsi/tcmu-runner/pull/644
• https://ubuntu.com/security/notices/USN-4694-1
• https://ubuntu.com/security/notices/USN-4713-1
• https://ubuntu.com/security/notices/USN-4711-1
• https://ubuntu.com/security/notices/USN-4709-1
• https://ubuntu.com/security/notices/USN-4713-2
• https://ubuntu.com/security/notices/USN-4753-1
• https://ubuntu.com/security/notices/USN-4901-1
• NVD
• Launchpad
• Debian