Canonical Ubuntu Linux 20.04 Lts

It was discovered that read_file() in apport/hookutils.py would follow symbolic links or open FIFOs. When this function is used by the xorg-hwe-18.04 package apport hooks, it could expose private data to other local users.

It was discovered that read_file() in apport/hookutils.py would follow symbolic links or open FIFOs. When this function is used by the xorg package apport hooks, it could expose private data to other local users.

It was discovered that read_file() in apport/hookutils.py would follow symbolic links or open FIFOs. When this function is used by the openjdk-17 package apport hooks, it could expose private data to other local users.

It was discovered that read_file() in apport/hookutils.py would follow symbolic links or open FIFOs. When this function is used by the openjdk-16 package apport hooks, it could expose private data to other local users.

It was discovered that read_file() in apport/hookutils.py would follow symbolic links or open FIFOs. When this function is used by the openjdk-15 package apport hooks, it could expose private data to other local users.

It was discovered that read_file() in apport/hookutils.py would follow symbolic links or open FIFOs. When this function is used by the openjdk-14 package apport hooks, it could expose private data to other local users.

It was discovered that read_file() in apport/hookutils.py would follow symbolic links or open FIFOs. When this function is used by the openjdk-13 package apport hooks, it could expose private data to other local users.

It was discovered that read_file() in apport/hookutils.py would follow symbolic links or open FIFOs. When this function is used by the openjdk-8 package apport hooks, it could expose private data to other local users.

It was discovered that read_file() in apport/hookutils.py would follow symbolic links or open FIFOs. When this function is used by the openjdk-lts package apport hooks, it could expose private data to other local users.

The io_uring subsystem in the Linux kernel allowed the MAX_RW_COUNT limit to be bypassed in the PROVIDE_BUFFERS operation, which led to negative values being usedin mem_rw when reading /proc//mem. This could be used to create a heap overflow leading to arbitrary code execution in the kernel. It was addressed via commit d1f82808877b ("io_uring: truncate lengths larger than MAX_RW_COUNT on provide buffers") (v5.13-rc1) and backported to the stable kernels in v5.12.4, v5.11.21, and v5.10.37. It was introduced in ddf0322db79c ("io_uring: add IORING_OP_PROVIDE_BUFFERS") (v5.7-rc1).

The eBPF ALU32 bounds tracking for bitwise ops (AND, OR and XOR) in the Linux kernel did not properly update 32-bit bounds, which could be turned into out of bounds reads and writes in the Linux kernel and therefore, arbitrary code execution. This issue was fixed via commit 049c4e13714e ("bpf: Fix alu32 const subreg bound tracking on bitwise operations") (v5.13-rc4) and backported to the stable kernels in v5.12.4, v5.11.21, and v5.10.37. The AND/OR issues were introduced by commit 3f50f132d840 ("bpf: Verifier, do explicit ALU32 bounds tracking") (5.7-rc1) and the XOR variant was introduced by 2921c90d4718 ("bpf:Fix a verifier failure with xor") ( 5.10-rc1).

The eBPF RINGBUF bpf_ringbuf_reserve() function in the Linux kernel did not check that the allocated size was smaller than the ringbuf size, allowing an attacker to perform out-of-bounds writes within the kernel and therefore, arbitrary code execution. This issue was fixed via commit 4b81ccebaeee ("bpf, ringbuf: Deny reserve of buffers larger than ringbuf") (v5.13-rc4) and backported to the stable kernels in v5.12.4, v5.11.21, and v5.10.37. It was introduced via 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it") (v5.8-rc1).

The overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces the setting of file capabilities on files in an underlying file system. Due to the combination of unprivileged user namespaces along with a patch carried in the Ubuntu kernel to allow unprivileged overlay mounts, an attacker could use this to gain elevated privileges.

Shiftfs, an out-of-tree stacking file system included in Ubuntu Linux kernels, did not properly handle faults occurring during copy_from_user() correctly. These could lead to either a double-free situation or memory not being freed at all. An attacker could use this to cause a denial of service (kernel memory exhaustion) or gain privileges via executing arbitrary code. AKA ZDI-CAN-13562.

Overlayfs did not properly perform permission checking when copying up files in an overlayfs and could be exploited from within a user namespace, if, for example, unprivileged user namespaces were allowed. It was possible to have a file not readable by an unprivileged user to be copied to a mountpoint controlled by the user, like a removable device. This was introduced in kernel version 4.19 by commit d1d04ef ("ovl: stack file ops"). This was fixed in kernel version 5.8 by commits 56230d9 ("ovl: verify permissions in ovl_path_open()"), 48bd024 ("ovl: switch to mounter creds in readdir") and 05acefb ("ovl: check permission to open real file"). Additionally, commits 130fdbc ("ovl: pass correct flags for opening real directory") and 292f902 ("ovl: call secutiry hook in ovl_real_ioctl()") in kernel 5.8 might also be desired or necessary. These additional commits introduced a regression in overlay mounts within user namespaces which prevented access to files with ownership outside of the user namespace. This regression was mitigated by subsequent commit b6650da ("ovl: do not fail because of O_NOATIMEi") in kernel 5.11.

Use-after-free vulnerability in the Linux kernel exploitable by a local attacker due to reuse of a DCCP socket with an attached dccps_hc_tx_ccid object as a listener after being released. Fixed in Ubuntu Linux kernel 5.4.0-51.56, 5.3.0-68.63, 4.15.0-121.123, 4.4.0-193.224, 3.13.0.182.191 and 3.2.0-149.196.

GNOME gdk-pixbuf (aka GdkPixbuf) before 2.42.2 allows a denial of service (infinite loop) in lzw.c in the function write_indexes. if c->self_code equals 10, self->code_table[10].extends will assign the value 11 to c. The next execution in the loop will assign self->code_table[11].extends to c, which will give the value of 10. This will make the loop run infinitely. This bug can, for example, be triggered by calling this function with a GIF image with LZW compression that is crafted in a special way.

Aptdaemon performed policykit checks after interacting with potentially untrusted files with elevated privileges. This affected versions prior to 1.1.1+bzr982-0ubuntu34.1, 1.1.1+bzr982-0ubuntu32.3, 1.1.1+bzr982-0ubuntu19.5, 1.1.1+bzr982-0ubuntu14.5.

The aptdaemon DBus interface disclosed file existence disclosure by setting Terminal/DebconfSocket properties, aka GHSL-2020-192 and GHSL-2020-196. This affected versions prior to 1.1.1+bzr982-0ubuntu34.1, 1.1.1+bzr982-0ubuntu32.3, 1.1.1+bzr982-0ubuntu19.5, 1.1.1+bzr982-0ubuntu14.5.

An Ubuntu-specific patch in PulseAudio created a race condition where the snap policy module would fail to identify a client connection from a snap as coming from a snap if SCM_CREDENTIALS were missing, allowing the snap to connect to PulseAudio without proper confinement. This could be exploited by an attacker to expose sensitive information. Fixed in 1:13.99.3-1ubuntu2, 1:13.99.2-1ubuntu2.1, 1:13.99.1-1ubuntu3.8, 1:11.1-1ubuntu7.11, and 1:8.0-0ubuntu3.15.

PackageKit's apt backend mistakenly treated all local debs as trusted. The apt security model is based on repository trust and not on the contents of individual files. On sites with configured PolicyKit rules this may allow users to install malicious packages.

PackageKit provided detailed error messages to unprivileged callers that exposed information about file presence and mimetype of files that the user would be unable to determine on its own.

Ubuntu's packaging of libvirt in 20.04 LTS created a control socket with world read and write permissions. An attacker could use this to overwrite arbitrary files or execute arbitrary code.

In containerd (an industry-standard container runtime) before version 1.2.14 there is a credential leaking vulnerability. If a container image manifest in the OCI Image format or Docker Image V2 Schema 2 format includes a URL for the location of a specific image layer (otherwise known as a “foreign layer†), the default containerd resolver will follow that URL to attempt to download it. In v1.2.x but not 1.3.0 or later, the default containerd resolver will provide its authentication credentials if the server where the URL is located presents an HTTP 401 status code along with registry-specific HTTP headers. If an attacker publishes a public image with a manifest that directs one of the layers to be fetched from a web server they control and they trick a user or system into pulling the image, they can obtain the credentials used for pulling that image. In some cases, this may be the user's username and password for the registry. In other cases, this may be the credentials attached to the cloud virtual instance which can grant access to other cloud resources in the account. The default containerd resolver is used by the cri-containerd plugin (which can be used by Kubernetes), the ctr development tool, and other client programs that have explicitly linked against it. This vulnerability has been fixed in containerd 1.2.14. containerd 1.3 and later are not affected. If you are using containerd 1.3 or later, you are not affected. If you are using cri-containerd in the 1.2 series or prior, you should ensure you only pull images from trusted sources. Other container runtimes built on top of containerd but not using the default resolver (such as Docker) are not affected.

A flaw was found in the Linux kernel in versions before 5.9-rc7. Traffic between two Geneve endpoints may be unencrypted when IPsec is configured to encrypt traffic for the specific UDP port used by the GENEVE tunnel allowing anyone between the two endpoints to read the traffic unencrypted. The main threat from this vulnerability is to data confidentiality.