SynopsisThe remote Amazon Linux AMI host is missing a security update.
DescriptionThe version of kernel installed on the remote host is prior to 4.14.225-121.357. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS-2021-1487 advisory.
- An issue was discovered in the Linux kernel 3.11 through 5.10.16, as used by Xen. To service requests to the PV backend, the driver maps grant references provided by the frontend. In this process, errors may be encountered. In one case, an error encountered earlier might be discarded by later processing, resulting in the caller assuming successful mapping, and hence subsequent operations trying to access space that wasn't mapped. In another case, internal state would be insufficiently updated, preventing safe recovery from the error. This affects drivers/block/xen-blkback/blkback.c. (CVE-2021-26930)
- An issue was discovered in the Linux kernel 2.6.39 through 5.10.16, as used in Xen. Block, net, and SCSI backends consider certain errors a plain bug, deliberately causing a kernel crash. For errors potentially being at least under the influence of guests (such as out of memory conditions), it isn't correct to assume a plain bug. Memory allocations potentially causing such crashes occur only when Linux is running in PV mode, though. This affects drivers/block/xen-blkback/blkback.c and drivers/xen/xen-scsiback.c.
- An issue was discovered in the Linux kernel 3.2 through 5.10.16, as used by Xen. Grant mapping operations often occur in batch hypercalls, where a number of operations are done in a single hypercall, the success or failure of each one is reported to the backend driver, and the backend driver then loops over the results, performing follow-up actions based on the success or failure of each operation. Unfortunately, when running in PV mode, the Linux backend drivers mishandle this: Some errors are ignored, effectively implying their success from the success of related batch elements. In other cases, errors resulting from one batch element lead to further batch elements not being inspected, and hence successful ones to not be possible to properly unmap upon error recovery. Only systems with Linux backends running in PV mode are vulnerable. Linux backends run in HVM / PVH modes are not vulnerable. This affects arch/*/xen/p2m.c and drivers/xen/gntdev.c. (CVE-2021-26932)
- An issue was discovered in the Linux kernel through 5.11.3. A kernel pointer leak can be used to determine the address of the iscsi_transport structure. When an iSCSI transport is registered with the iSCSI subsystem, the transport's handle is available to unprivileged users via the sysfs file system, at /sys/class/iscsi_transport/$TRANSPORT_NAME/handle. When read, the show_transport_handle function (in drivers/scsi/scsi_transport_iscsi.c) is called, which leaks the handle. This handle is actually the pointer to an iscsi_transport struct in the kernel module's global variables. (CVE-2021-27363)
- An issue was discovered in the Linux kernel through 5.11.3. drivers/scsi/scsi_transport_iscsi.c is adversely affected by the ability of an unprivileged user to craft Netlink messages. (CVE-2021-27364)
- An issue was discovered in the Linux kernel through 5.11.3. Certain iSCSI data structures do not have appropriate length constraints or checks, and can exceed the PAGE_SIZE value. An unprivileged user can send a Netlink message that is associated with iSCSI, and has a length up to the maximum length of a Netlink message. (CVE-2021-27365)
- An issue was discovered in the Linux kernel through 5.11.3, as used with Xen PV. A certain part of the netback driver lacks necessary treatment of errors such as failed memory allocations (as a result of changes to the handling of grant mapping errors). A host OS denial of service may occur during misbehavior of a networking frontend driver. NOTE: this issue exists because of an incomplete fix for CVE-2021-26931.
Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.
SolutionRun 'yum update kernel' to update your system.
File Name: ala_ALAS-2021-1487.nasl
Supported Sensors: Frictionless Assessment Agent, Frictionless Assessment AWS, Nessus Agent
Temporal Vector: E:U/RL:OF/RC:C
Temporal Vector: E:U/RL:O/RC:C
CPE: p-cpe:/a:amazon:linux:kernel, p-cpe:/a:amazon:linux:kernel-debuginfo, p-cpe:/a:amazon:linux:kernel-debuginfo-common-i686, p-cpe:/a:amazon:linux:kernel-debuginfo-common-x86_64, p-cpe:/a:amazon:linux:kernel-devel, p-cpe:/a:amazon:linux:kernel-headers, p-cpe:/a:amazon:linux:kernel-tools, p-cpe:/a:amazon:linux:kernel-tools-debuginfo, p-cpe:/a:amazon:linux:kernel-tools-devel, p-cpe:/a:amazon:linux:perf, p-cpe:/a:amazon:linux:perf-debuginfo, cpe:/o:amazon:linux
Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list
Exploit Ease: No known exploits are available
Patch Publication Date: 3/18/2021
Vulnerability Publication Date: 2/16/2021