The Debian pg_ctlcluster, pg_createcluster, and pg_upgradecluster scripts, as distributed in the Debian postgresql-common package before 181+deb9u1 for PostgreSQL (and other packages related to Debian and Ubuntu), handled symbolic links insecurely, which could result in local denial of service by overwriting arbitrary files.

A flaw was found in chrony versions before 3.5.1 when creating the PID file under the /var/run/chrony folder. The file is created during chronyd startup while still running as the root user, and when it's opened for writing, chronyd does not check for an existing symbolic link with the same file name. This flaw allows an attacker with privileged access to create a symlink with the default PID file name pointing to any destination file in the system, resulting in data loss and a denial of service due to the path traversal.

There is an issue with grub2 before version 2.06 while handling symlink on ext filesystems. A filesystem containing a symbolic link with an inode size of UINT32_MAX causes an arithmetic overflow leading to a zero-sized memory allocation with subsequent heap-based buffer overflow.

There is an issue on grub2 before version 2.06 at function read_section_as_string(). It expects a font name to be at max UINT32_MAX - 1 length in bytes but it doesn't verify it before proceed with buffer allocation to read the value from the font value. An attacker may leverage that by crafting a malicious font file which has a name with UINT32_MAX, leading to read_section_as_string() to an arithmetic overflow, zero-sized allocation and further heap-based buffer overflow.

An issue was discovered in the Linux kernel through 5.6.2. mpol_parse_str in mm/mempolicy.c has a stack-based out-of-bounds write because an empty nodelist is mishandled during mount option parsing, aka CID-aa9f7d5172fa. NOTE: Someone in the security community disagrees that this is a vulnerability because the issue “is a bug in parsing mount options which can only be specified by a privileged user, so triggering the bug does not grant any powers not already held.”

Vulnerability in the MySQL Server component of Oracle MySQL (subcomponent: Server: Security: Privileges). Supported versions that are affected are 5.6.44 and prior, 5.7.26 and prior and 8.0.16 and prior. Easily exploitable vulnerability allows high privileged attacker with logon to the infrastructure where MySQL Server executes to compromise MySQL Server. Successful attacks of this vulnerability can result in unauthorized ability to cause a hang or frequently repeatable crash (complete DOS) of MySQL Server as well as unauthorized update, insert or delete access to some of MySQL Server accessible data. CVSS 3.0 Base Score 5.1 (Integrity and Availability impacts). CVSS Vector: (CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:H).

In shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, shiftfs_btrfs_ioctl_fd_replace() calls fdget(oldfd), then without further checks passes the resulting file* into shiftfs_real_fdget(), which casts file->private_data, a void* that points to a filesystem-dependent type, to a "struct shiftfs_file_info *". As the private_data is not required to be a pointer, an attacker can use this to cause a denial of service or possibly execute arbitrary code.

In shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, shiftfs_btrfs_ioctl_fd_replace() installs an fd referencing a file from the lower filesystem without taking an additional reference to that file. After the btrfs ioctl completes this fd is closed, which then puts a reference to that file, leading to a refcount underflow.

Overlayfs in the Linux kernel and shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, both replace vma->vm_file in their mmap handlers. On error the original value is not restored, and the reference is put for the file to which vm_file points. On upstream kernels this is not an issue, as no callers dereference vm_file following after call_mmap() returns an error. However, the aufs patchs change mmap_region() to replace the fput() using a local variable with vma_fput(), which will fput() vm_file, leading to a refcount underflow.

arch/arm64/kvm/guest.c in KVM in the Linux kernel before 4.18.12 on the arm64 platform mishandles the KVM_SET_ON_REG ioctl. This is exploitable by attackers who can create virtual machines. An attacker can arbitrarily redirect the hypervisor flow of control (with full register control). An attacker can also cause a denial of service (hypervisor panic) via an illegal exception return. This occurs because of insufficient restrictions on userspace access to the core register file, and because PSTATE.M validation does not prevent unintended execution modes.

Off-by-one error in the ecryptfs_decode_from_filename function in fs/ecryptfs/crypto.c in the eCryptfs subsystem in the Linux kernel before 3.18.2 allows local users to cause a denial of service (buffer overflow and system crash) or possibly gain privileges via a crafted filename.

Multiple directory traversal vulnerabilities in GNU binutils 2.24 and earlier allow local users to delete arbitrary files via a .. (dot dot) or full path name in an archive to (1) strip or (2) objcopy or create arbitrary files via (3) a .. (dot dot) or full path name in an archive to ar.

The Ubuntu AccountsService package before 0.6.14-1git1ubuntu1.1 does not properly drop privileges when changing language settings, which allows local users to modify arbitrary files via unspecified vectors.

The btrfs_ioctl_clone function in fs/btrfs/ioctl.c in the Linux kernel before 2.6.35 allows local users to overwrite an append-only file via a (1) BTRFS_IOC_CLONE or (2) BTRFS_IOC_CLONE_RANGE ioctl call that specifies this file as a donor.

The poll_mode_io file for the megaraid_sas driver in the Linux kernel 2.6.31.6 and earlier has world-writable permissions, which allows local users to change the I/O mode of the driver by modifying this file.

is_closing_session() allows users to create arbitrary tcp dbus connections

On desktop, Ubuntu UI Toolkit's StateSaver would serialise data on tmp/ files which an attacker could use to expose potentially sensitive data. StateSaver would also open files without the O_EXCL flag. An attacker could exploit this to launch a symlink attack, though this is partially mitigated by symlink and hardlink restrictions in Ubuntu. Fixed in 1.1.1188+14.10.20140813.4-0ubuntu1.

Apport creates a world writable lock file with root ownership in the world writable /var/lock/apport directory. If the apport/ directory does not exist (this is not uncommon as /var/lock is a tmpfs), it will create the directory, otherwise it will simply continue execution using the existing directory. This allows for a symlink attack if an attacker were to create a symlink at /var/lock/apport, changing apport's lock file location. This file could then be used to escalate privileges, for example. Fixed in versions 2.20.1-0ubuntu2.23, 2.20.9-0ubuntu7.14, 2.20.11-0ubuntu8.8 and 2.20.11-0ubuntu22.

Puppet before 3.3.3 and 3.4 before 3.4.1 and Puppet Enterprise (PE) before 2.8.4 and 3.1 before 3.1.1 allows local users to overwrite arbitrary files via a symlink attack on unspecified files.

In KDE Ark before 20.08.1, a crafted TAR archive with symlinks can install files outside the extraction directory, as demonstrated by a write operation to a user's home directory.

Net-SNMP through 5.7.3 allows Escalation of Privileges because of UNIX symbolic link (symlink) following.

fr-archive-libarchive.c in GNOME file-roller through 3.36.1 allows Directory Traversal during extraction because it lacks a check of whether a file's parent is a symlink to a directory outside of the intended extraction location.

init_tmp in TeeJee.FileSystem.vala in Timeshift before 20.03 unsafely reuses a preexisting temporary directory in the predictable location /tmp/timeshift. It follows symlinks in this location or uses directories owned by unprivileged users. Because Timeshift also executes scripts under this location, an attacker can attempt to win a race condition to replace scripts created by Timeshift with attacker-controlled scripts. Upon success, an attacker-controlled script is executed with full root privileges. This logic is practically always triggered when Timeshift runs regardless of the command-line arguments used.

checkinstall 1.6.2, when used to create a package that contains a symlink, may trigger the creation of a mode 0777 executable file.

Lintian before 2.5.12 allows remote attackers to gather information about the "host" system using crafted symlinks.

snap-confine in snapd before 2.38 incorrectly set the ownership of a snap application to the uid and gid of the first calling user. Consequently, that user had unintended access to a private /tmp directory.

Kevin Backhouse discovered that apport would read a user-supplied configuration file with elevated privileges. By replacing the file with a symbolic link, a user could get apport to read any file on the system as root, with unknown consequences.

dmrc.c in Light Display Manager (aka LightDM) before 1.1.1 allows local users to read arbitrary files via a symlink attack on ~/.dmrc.

An insecure symlink following vulnerability exists in Canonical ubuntu-pro-client (formerly ubuntu-advantage-tools) within the pro collect-logs command framework. The utility creates or utilizes predictable temporary file paths or user-accessible log directories when gathering diagnostic information without verifying the file type or ownership. An unprivileged local attacker can exploit this behavior by creating a symbolic link (symlink) at a predictable destination path pointing to an arbitrary, root-readable file (such as /etc/shadow or private files within /root). When a root administrator or operator subsequently executes the pro collect-logs command, the tool follows the user-controlled symlink, reads the target file, and compresses its contents into the resulting diagnostic support archive. Because the output archive remains readable by the unprivileged user, the attacker can extract and read the sensitive root-owned files, leading to a complete information disclosure of system secrets.

systemd-tmpfiles in systemd through 237 mishandles symlinks present in non-terminal path components, which allows local users to obtain ownership of arbitrary files via vectors involving creation of a directory and a file under that directory, and later replacing that directory with a symlink. This occurs even if the fs.protected_symlinks sysctl is turned on.

w3m through 0.5.3 does not properly handle temporary files when the ~/.w3m directory is unwritable, which allows a local attacker to craft a symlink attack to overwrite arbitrary files.

The printing process can bypass local access protections to read files available through symlinks, bypassing local file restrictions. The printing process requires files in a specific format so arbitrary data cannot be read but it is possible that some local file information could be exposed. This vulnerability affects Firefox < 58.

In the cron package through 3.0pl1-128 on Debian, and through 3.0pl1-128ubuntu2 on Ubuntu, the postinst maintainer script allows for group-crontab-to-root privilege escalation via symlink attacks against unsafe usage of the chown and chmod programs.

In libXfont before 1.5.4 and libXfont2 before 2.0.3, a local attacker can open (but not read) files on the system as root, triggering tape rewinds, watchdogs, or similar mechanisms that can be triggered by opening files.

dbus before 1.10.28, 1.12.x before 1.12.16, and 1.13.x before 1.13.12, as used in DBusServer in Canonical Upstart in Ubuntu 14.04 (and in some, less common, uses of dbus-daemon), allows cookie spoofing because of symlink mishandling in the reference implementation of DBUS_COOKIE_SHA1 in the libdbus library. (This only affects the DBUS_COOKIE_SHA1 authentication mechanism.) A malicious client with write access to its own home directory could manipulate a ~/.dbus-keyrings symlink to cause a DBusServer with a different uid to read and write in unintended locations. In the worst case, this could result in the DBusServer reusing a cookie that is known to the malicious client, and treating that cookie as evidence that a subsequent client connection came from an attacker-chosen uid, allowing authentication bypass.

snap-confine as included in snapd before 2.39 did not guard against symlink races when performing the chdir() to the current working directory of the calling user, aka a "cwd restore permission bypass."

The postinst script in the tomcat6 package before 6.0.45+dfsg-1~deb7u4 on Debian wheezy, before 6.0.35-1ubuntu3.9 on Ubuntu 12.04 LTS and on Ubuntu 14.04 LTS; the tomcat7 package before 7.0.28-4+deb7u8 on Debian wheezy, before 7.0.56-3+deb8u6 on Debian jessie, before 7.0.52-1ubuntu0.8 on Ubuntu 14.04 LTS, and on Ubuntu 12.04 LTS, 16.04 LTS, and 16.10; and the tomcat8 package before 8.0.14-1+deb8u5 on Debian jessie, before 8.0.32-1ubuntu1.3 on Ubuntu 16.04 LTS, before 8.0.37-1ubuntu0.1 on Ubuntu 16.10, and before 8.0.38-2ubuntu1 on Ubuntu 17.04 might allow local users with access to the tomcat account to obtain sensitive information or gain root privileges via a symlink attack on the Catalina localhost directory.

The MOTD update script in the base-files package in Ubuntu 18.04 LTS before 10.1ubuntu2.2, and Ubuntu 18.10 before 10.1ubuntu6 incorrectly handled temporary files. A local attacker could use this issue to cause a denial of service, or possibly escalate privileges if kernel symlink restrictions were disabled.

sosreport in SoS 3.x allows local users to obtain sensitive information from sosreport files or gain privileges via a symlink attack on an archive file in a temporary directory, as demonstrated by sosreport-$hostname-$date.tar in /tmp/sosreport-$hostname-$date.

lxc-start in lxc before 1.0.8 and 1.1.x before 1.1.4 allows local container administrators to escape AppArmor confinement via a symlink attack on a (1) mount target or (2) bind mount source.

kernel_crashdump in Apport before 2.19 allows local users to cause a denial of service (disk consumption) or possibly gain privileges via a (1) symlink or (2) hard link attack on /var/crash/vmcore.log.

In Perl through 5.26.2, the Archive::Tar module allows remote attackers to bypass a directory-traversal protection mechanism, and overwrite arbitrary files, via an archive file containing a symlink and a regular file with the same name.

DistUpgrade/DistUpgradeViewKDE.py in Update Manager before 1:0.87.31.1, 1:0.134.x before 1:0.134.11.1, 1:0.142.x before 1:0.142.23.1, 1:0.150.x before 1:0.150.5.1, and 1:0.152.x before 1:0.152.25.5 does not properly create temporary files, which allows local users to obtain the XAUTHORITY file content for a user via a symlink attack on the temporary file.

pam_motd (aka the MOTD module) in libpam-modules before 1.1.0-2ubuntu1.1 in PAM on Ubuntu 9.10 and libpam-modules before 1.1.1-2ubuntu5 in PAM on Ubuntu 10.04 LTS allows local users to change the ownership of arbitrary files via a symlink attack on .cache in a user's home directory, related to "user file stamps" and the motd.legal-notice file.

The distcheck rule in dist-check.mk in GNU coreutils 5.2.1 through 8.1 allows local users to gain privileges via a symlink attack on a file in a directory tree under /tmp.

In snapd versions prior to 2.62, snapd failed to properly check the destination of symbolic links when extracting a snap. The snap format is a squashfs file-system image and so can contain symbolic links and other file types. Various file entries within the snap squashfs image (such as icons and desktop files etc) are directly read by snapd when it is extracted. An attacker who could convince a user to install a malicious snap which contained symbolic links at these paths could then cause snapd to write out the contents of the symbolic link destination into a world-readable directory. This in-turn could allow an unprivileged user to gain access to privileged information.

MySQL before 5.0.67 allows local users to bypass certain privilege checks by calling CREATE TABLE on a MyISAM table with modified (1) DATA DIRECTORY or (2) INDEX DIRECTORY arguments that are originally associated with pathnames without symlinks, and that can point to tables created at a future time at which a pathname is modified to contain a symlink to a subdirectory of the MySQL home data directory. NOTE: this vulnerability exists because of an incomplete fix for CVE-2008-4097.

snapd 2.54.2 did not properly validate the location of the snap-confine binary. A local attacker who can hardlink this binary to another location to cause snap-confine to execute other arbitrary binaries and hence gain privilege escalation. Fixed in snapd versions 2.54.3+18.04, 2.54.3+20.04 and 2.54.3+21.10.1

Race condition in cpio 2.6 and earlier allows local users to modify permissions of arbitrary files via a hard link attack on a file while it is being decompressed, whose permissions are changed by cpio after the decompression is complete.