Ubuntu Security Notice 3836-2 - USN-3836-1 fixed vulnerabilities in the Linux kernel for Ubuntu 18.04 LTS. This update provides the corresponding updates for the Linux Hardware Enablement kernel from Ubuntu 18.04 LTS for Ubuntu 16.04 LTS. Jann Horn discovered that the Linux kernel mishandles mapping UID or GID ranges inside nested user namespaces in some situations. A local attacker could use this to bypass access controls on resources outside the namespace. Various other issues were also addressed.
a16f0a83e02d3a223fa194bb6e8753f511a0439bdb62c486b7cff7d861d45961Ubuntu Security Notice 3836-1 - Jann Horn discovered that the Linux kernel mishandles mapping UID or GID ranges inside nested user namespaces in some situations. A local attacker could use this to bypass access controls on resources outside the namespace. Philipp Wendler discovered that the overlayfs implementation in the Linux kernel did not properly verify the directory contents permissions from within a unprivileged user namespace. A local attacker could use this to expose sensitive information. Various other issues were also addressed.
381aa075aa2708693455c43a91237a24db2a3c496d9a9b5a2b1927429cfebeb4Ubuntu Security Notice 3835-1 - Jann Horn discovered that the procfs file system implementation in the Linux kernel did not properly restrict the ability to inspect the kernel stack of an arbitrary task. A local attacker could use this to expose sensitive information. Jann Horn discovered that the mremap system call in the Linux kernel did not properly flush the TLB when completing, potentially leaving access to a physical page after it has been released to the page allocator. A local attacker could use this to cause a denial of service , expose sensitive information, or possibly execute arbitrary code. Various other issues were also addressed.
0d98e117a7daeada246e248b8dd8991176e44f3691e448cdd5919caf358556aaUbuntu Security Notice 3833-1 - Jann Horn discovered that the Linux kernel mishandles mapping UID or GID ranges inside nested user namespaces in some situations. A local attacker could use this to bypass access controls on resources outside the namespace. Philipp Wendler discovered that the overlayfs implementation in the Linux kernel did not properly verify the directory contents permissions from within a unprivileged user namespace. A local attacker could use this to expose sensitive information. Various other issues were also addressed.
a245ddd2e063e75ae9b8cd656c2ba843ed10ef466025e17abe119b7bfbe3080aUbuntu Security Notice 3832-1 - Jann Horn discovered that the procfs file system implementation in the Linux kernel did not properly restrict the ability to inspect the kernel stack of an arbitrary task. A local attacker could use this to expose sensitive information. Jann Horn discovered that the mremap system call in the Linux kernel did not properly flush the TLB when completing, potentially leaving access to a physical page after it has been released to the page allocator. A local attacker could use this to cause a denial of service , expose sensitive information, or possibly execute arbitrary code. Various other issues were also addressed.
b57e39d7a6b2621e28ea09c25523ef6ffe045219afabe19ad27f96586c416cd1This Metasploit module exploits a vulnerability in Linux kernels 4.15.0 to 4.18.18, and 4.19.0 to 4.19.1, where broken uid/gid mappings between nested user namespaces and kernel uid/gid mappings allow elevation to root (CVE-2018-18955). The target system must have unprivileged user namespaces enabled and the newuidmap and newgidmap helpers installed (from uidmap package). This Metasploit module has been tested successfully on: Fedora Workstation 28 kernel 4.16.3-301.fc28.x86_64; Kubuntu 18.04 LTS kernel 4.15.0-20-generic (x86_64); Linux Mint 19 kernel 4.15.0-20-generic (x86_64); Ubuntu Linux 18.04.1 LTS kernel 4.15.0-20-generic (x86_64).
c991b79ae898a222baf512ec75bc5ae786505466b71b6453fd873f6b5482343cLinux has a broken uid/gid mapping for nested user namespaces with greater than 5 ranges.
53da54afe1913539df473ff36059802468d06980a436040ba7120c6c26f62627
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