Several vulnerabilities have been discovered in the Linux kernel that may lead to a privilege escalation, denial of service or information leaks.
Multiple researchers have discovered a vulnerability in the way the Intel processor designs have implemented speculative execution of instructions in combination with handling of page-faults. This flaw could allow an attacker controlling an unprivileged process to read memory from arbitrary (non-user controlled) addresses, including from the kernel and all other processes running on the system or cross guest/host boundaries to read host memory. This issue covers only attackers running normal processes. A related issue (CVE-2018-3646) exists with KVM guests, and is not yet fixed.
Multiple researchers have discovered that Speculative Store Bypass (SSB), a feature implemented in many processors, could be used to read sensitive information from another context. In particular, code in a software sandbox may be able to read sensitive information from outside the sandbox. This issue is also known as Spectre variant 4. This update allows the issue to be mitigated on some x86 processors by disabling SSB. This requires an update to the processor's microcode, which is non-free. DLA 1446-1 and DLA 1506-1 provided this for some Intel processors. For other processors, it may be included in an update to the system BIOS or UEFI firmware, or in a future update to the intel-microcode or amd64-microcode packages. Disabling SSB can reduce performance significantly, so by default it is only done in tasks that use the seccomp feature. Applications that require this mitigation should request it explicitly through the prctl() system call. Users can control where the mitigation is enabled with the spec_store_bypass_disable kernel parameter.
Juha-Matti Tilli discovered a flaw in the way the Linux kernel handled reassembly of fragmented IPv4 and IPv6 packets. A remote attacker can take advantage of this flaw to trigger time and calculation expensive fragment reassembly algorithms by sending specially crafted packets, leading to remote denial of service. This is mitigated by reducing the default limits on memory usage for incomplete fragmented packets. The same mitigation can be achieved without the need to reboot, by setting the sysctls: net.ipv4.ipfrag_low_thresh = 196608 net.ipv6.ip6frag_low_thresh = 196608 net.ipv4.ipfrag_high_thresh = 262144 net.ipv6.ip6frag_high_thresh = 262144 The default values may still be increased by local configuration if necessary.
A memory leak in the irda_bind function in the irda subsystem was discovered. A local user can take advantage of this flaw to cause a denial of service (memory consumption).
A flaw was discovered in the irda_setsockopt function in the irda subsystem, allowing a local user to cause a denial of service (use-after-free and system crash).
Brian Belleville discovered a flaw in the fd_locked_ioctl function in the floppy driver in the Linux kernel. The floppy driver copies a kernel pointer to user memory in response to the FDGETPRM ioctl. A local user with access to a floppy drive device can take advantage of this flaw to discover the location kernel code and data.
It was discovered that the Bluetooth HIDP implementation did not correctly check the length of received report messages. A paired HIDP device could use this to cause a buffer overflow, leading to denial of service (memory corruption or crash) or potentially remote code execution.
It was discovered that the HID events interface in debugfs did not correctly limit the length of copies to user buffers. A local user with access to these files could use this to cause a denial of service (memory corruption or crash) or possibly for privilege escalation. However, by default debugfs is only accessible by the root user.
A physically present attacker who unplugs a SAS cable can cause a denial of service (memory leak and WARN).
CVE-2018-10323, CVE-2018-13093, CVE-2018-13094
Wen Xu from SSLab at Gatech reported several NULL pointer dereference flaws that may be triggered when mounting and operating a crafted XFS volume. An attacker able to mount arbitrary XFS volumes could use this to cause a denial of service (crash).
CVE-2018-10876, CVE-2018-10877, CVE-2018-10878, CVE-2018-10879, CVE-2018-10880, CVE-2018-10881, CVE-2018-10882, CVE-2018-10883
Wen Xu from SSLab at Gatech reported that crafted ext4 volumes could trigger a crash or memory corruption. An attacker able to mount arbitrary ext4 volumes could use this for denial of service or possibly for privilege escalation.
It was discovered that the rawmidi kernel driver does not protect against concurrent access which leads to a double-realloc (double free) flaw. A local attacker can take advantage of this issue for privilege escalation.
Jann Horn discovered that the inode_init_owner function in fs/inode.c in the Linux kernel allows local users to create files with an unintended group ownership allowing attackers to escalate privileges by making a plain file executable and SGID.
Dr Silvio Cesare of InfoSect reported a potential integer overflow in the uvesafb driver. A local user with permission to access such a device might be able to use this for denial of service or privilege escalation.
Wen Xu from SSLab at Gatech reported a potential null pointer dereference in the F2FS implementation. An attacker able to mount arbitrary F2FS volumes could use this to cause a denial of service (crash).
Wen Xu from SSLab at Gatech reported a potential null pointer dereference in the HFS+ implementation. An attacker able to mount arbitrary HFS+ volumes could use this to cause a denial of service (crash).
Vincent Pelletier discovered a stack-based buffer overflow flaw in the chap_server_compute_md5() function in the iSCSI target code. An unauthenticated remote attacker can take advantage of this flaw to cause a denial of service or possibly to get a non-authorized access to data exported by an iSCSI target.
Qualys reported an integer overflow in the initialisation of the stack for ELF executables, which can cause the stack to overlap the argument or environment strings. A local user may use this to defeat environment variable filtering in setuid programs, leading to privilege escalation.
M. Vefa Bicakci and Andy Lutomirski discovered a flaw in the kernel exit code used on amd64 systems running as Xen PV guests. A local user could use this to cause a denial of service (crash).
A use-after-free bug was discovered in the InfiniBand communication manager. A local user could use this to cause a denial of service (crash or memory corruption) or possible for privilege escalation.
Esmaiel Mohammadian Koruyeh, Khaled Khasawneh, Chengyu Song, and Nael Abu-Ghazaleh, from University of California, Riverside, reported a variant of Spectre variant 2, dubbed SpectreRSB. A local user may be able to use this to read sensitive information from processes owned by other users.
Nadav Amit reported that some indirect function calls used in paravirtualised guests were vulnerable to Spectre variant 2. A local user may be able to use this to read sensitive information from the kernel.
Jann Horn discovered that the yurex driver did not correctly limit the length of copies to user buffers. A local user with access to a yurex device node could use this to cause a denial of service (memory corruption or crash) or possibly for privilege escalation.
It was discovered that the cdrom driver does not correctly validate the parameter to the CDROM_DRIVE_STATUS ioctl. A user with access to a cdrom device could use this to read sensitive information from the kernel or to cause a denial of service (crash).
Jann Horn discovered that the vmacache_flush_all function mishandles sequence number overflows. A local user can take advantage of this flaw to trigger a use-after-free, causing a denial of service (crash or memory corruption) or privilege escalation.
Since the kernel ABI and binary package names have changed, you will need to use an upgrade command that installs new dependencies, such as “apt-get dist-upgrade”.
For Debian 7 Wheezy, these problems have been fixed in version 3.16.59-1~deb7u1.
We recommend that you upgrade your linux packages.
Further information about Extended LTS security advisories can be found at: https://deb.freexian.com/extended-lts/