Debian DLA-1771-1 : linux-4.9 security update
High Nessus Plugin ID 124595
SynopsisThe remote Debian host is missing a security update.
DescriptionSeveral vulnerabilities have been discovered in the Linux kernel that may lead to a privilege escalation, denial of service or information leaks.
A use-after-free bug was found in the vhost driver for the Virtual Socket protocol. If this driver is used to communicate with a malicious virtual machine guest, the guest could read sensitive information from the host kernel.
A flaw was found in the NFS 4.1 client implementation. Mounting NFS shares in multiple network namespaces at the same time could lead to a user-after-free. Local users might be able to use this for denial of service (memory corruption or crash) or possibly for privilege escalation.
This can be mitigated by disabling unprivileged users from creating user namespaces, which is the default in Debian.
Hui Peng and Mathias Payer discovered a use-after-free bug in the USB audio driver. A physically present attacker able to attach a specially designed USB device could use this for privilege escalation.
Hui Peng and Mathias Payer discovered a missing bounds check in the hso USB serial driver. A physically present user able to attach a specially designed USB device could use this to read sensitive information from the kernel or to cause a denial of service (crash).
Hui Peng and Mathias Payer discovered missing bounds checks in the USB core. A physically present attacker able to attach a specially designed USB device could use this to cause a denial of service (crash) or possibly for privilege escalation.
It was discovered that Linux could forward aggregated network packets with a segmentation size too large for the output device. In the specific case of Broadcom NetXtremeII 10Gb adapters, this would result in a denial of service (firmware crash). This update adds a mitigation to the bnx2x driver for this hardware.
Shlomi Oberman, Yuli Shapiro and Karamba Security Ltd. research team discovered missing range checks in the Bluetooth L2CAP implementation.
If Bluetooth is enabled, a nearby attacker could use these to read sensitive information from the kernel.
Muyu Yu and Marcus Meissner reported that the CAN gateway implementation allowed the frame length to be modified, typically resulting in out-of-bounds memory-mapped I/O writes. On a system with CAN devices present, a local user with CAP_NET_ADMIN capability in the initial net namespace could use this to cause a crash (oops) or other hardware-dependent impact.
A potential infinite loop was discovered in the HID debugfs interface exposed under /sys/kernel/debug/hid. A user with access to these files could use this for denial of service.
This interface is only accessible to root by default, which fully mitigates the issue.
Jann Horn reported a use-after-free bug in KVM. A local user with access to /dev/kvm could use this to cause a denial of service (memory corruption or crash) or possibly for privilege escalation.
Jim Mattson and Felix Wilhelm reported a user-after-free bug in KVM's nested VMX implementation. On systems with Intel CPUs, a local user with access to /dev/kvm could use this to cause a denial of service (memory corruption or crash) or possibly for privilege escalation.
Nested VMX is disabled by default, which fully mitigates the issue.
Felix Wilhelm reported an information leak in KVM for x86. A local user with access to /dev/kvm could use this to read sensitive information from the kernel.
A bug was discovered in the kernel_read_file() function used to load firmware files. In certain error conditions it could leak memory, which might lead to a denial of service. This is probbaly not exploitable in a Debian system.
Jann Horn reported that privileged tasks could cause stack segments, including those in other processes, to grow downward to address 0. On systems lacking SMAP (x86) or PAN (ARM), this exacerbated other vulnerabilities: a NULL pointer dereference could be exploited for privilege escalation rather than only for denial of service.
For Debian 8 'Jessie', these problems have been fixed in version 4.9.168-1~deb8u1. This version also includes fixes for Debian bugs #904385, #918103, and #922306; and other fixes included in upstream stable updates.
We recommend that you upgrade your linux-4.9 and linux-latest-4.9 packages. You will need to use 'apt-get upgrade --with-new-pkgs' or 'apt upgrade' as the binary package names have changed.
NOTE: Tenable Network Security has extracted the preceding description block directly from the DLA security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
SolutionUpgrade the affected packages.