Fragnesia is a universal Linux local privilege escalation exploit, discovered by William Bowling with the V12 team. Fragnesia is a member of the Dirty Frag vulnerability class. This is a separate bug in the ESP/XFRM from dirtyfrag which has received its own patch. However, it is in the same surface and the mitigation is the same as for dirtyfrag.

It abuses a logic bug in the Linux XFRM ESP-in-TCP subsystem to achieve arbitrary byte writes into the kernel page cache of read-only files, without requiring any race condition.

The technique extends the page-cache write bug class that includes Dirty Pipe: when a TCP socket transitions to espintcp ULP mode after data has already been spliced from a file into the receive queue, the kernel processes the queued file pages as ESP ciphertext. The AES-GCM keystream byte at counter block position 2, byte 0 is XORed directly into the cached file page. By selecting the IV nonce to produce a desired keystream byte, any target byte in the file can be set to any value — one byte per trigger invocation.

The exploit builds a 256-entry lookup table mapping each possible keystream byte to its corresponding nonce, then iterates over a payload, firing the splice/ULP race for each byte that needs changing. It writes a small position-independent ELF stub (setresuid/setresgid/execve /bin/sh) over the first 192 bytes of /usr/bin/su in the page cache, then calls execve("/usr/bin/su") to obtain a root shell. The page cache modification is not backed to disk; the on-disk binary is untouched.

In the Linux kernel, the following vulnerability has been resolved:

crypto: algifaead - Revert to operating out-of-place

HID: core: zero-initialize the report buffer

In the Linux kernel, the following vulnerability has been resolved:

media: uvcvideo: Skip parsing frames of type UVCVSUNDEFINED in uvcparseformat

This can lead to out of bounds writes since frames of this type were not taken into account when calculating the size of the frames buffer in uvcparsestreaming.

In the Linux kernel, the following vulnerability has been resolved:

ALSA: usb-audio: Fix out of bounds reads when finding clock sources

The current USB-audio driver code doesn't check bLength of each descriptor at traversing for clock descriptors. That is, when a device provides a bogus descriptor with a shorter bLength, the driver might hit out-of-bounds reads.

For addressing it, this patch adds sanity checks to the validator functions for the clock descriptor traversal. When the descriptor length is shorter than expected, it's skipped in the loop.

For the clock source and clock multiplier descriptors, we can just check bLength against the sizeof() of each descriptor type. OTOH, the clock selector descriptor of UAC2 and UAC3 has an array of bNrInPins elements and two more fields at its tail, hence those have to be checked in addition to the sizeof() check.

In the Linux kernel, the following vulnerability has been resolved:

ALSA: usb-audio: Fix potential out-of-bound accesses for Extigy and Mbox devices

A bogus device can provide a bNumConfigurations value that exceeds the initial value used in usbgetconfiguration for allocating dev->config.

This can lead to out-of-bounds accesses later, e.g. in usbdestroyconfiguration.

Android contains an unspecified vulnerability in the kernel that allows for remote code execution. This vulnerability resides in Linux Kernel and could impact other products, including but not limited to Android OS.

A use-after-free flaw was found in nftables cross-table in the net/netfilter/nftablesapi.c function in the Linux kernel. This flaw allows a local, privileged attacker to cause a use-after-free problem at the time of table deletion, possibly leading to local privilege escalation.

In the Linux kernel, the following vulnerability has been resolved:

posix-cpu-timers: fix race between handleposixcputimers() and posixcputimerdel()

If an exiting non-autoreaping task has already passed exitnotify() and calls handleposixcputimers() from IRQ, it can be reaped by its parent or debugger right after unlocktasksighand().

If a concurrent posixcputimerdel() runs at that moment, it won't be able to detect timer->it.cpu.firing != 0: cputimertaskrcu() and/or locktasksighand() will fail.

Add the tsk->exitstate check into runposixcputimers() to fix this.

This fix is not needed if CONFIGPOSIXCPUTIMERSTASKWORK=y, because exittaskwork() is called before exitnotify(). But the check still makes sense, taskworkadd(&tsk->posixcputimerswork.work) will fail anyway in this case.

A flaw was found in the Linux kernel, where unauthorized access to the execution of the setuid file with capabilities was found in the Linux kernel’s OverlayFS subsystem in how a user copies a capable file from a nosuid mount into another mount. This uid mapping bug allows a local user to escalate their privileges on the system.

A use after free vulnerability exists in the ALSA PCM package in the Linux Kernel. SNDRVCTLIOCTLELEM{READ|WRITE}32 is missing locks that can be used in a use-after-free that can result in a priviledge escalation to gain ring0 access from the system user. We recommend upgrading past commit 56b88b50565cd8b946a2d00b0c83927b7ebb055e

A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copypagetoiterpipe and pushpipe functions in the Linux kernel and could thus contain stale values. An unprivileged local user could use this flaw to write to pages in the page cache backed by read only files and as such escalate their privileges on the system.

A vulnerability was found in cgroupreleaseagentwrite in kernel/cgroup/cgroup-v1.c in the Linux kernel. In this flaw, under certain circumstances, the cgroups v1 releaseagent feature can be used to escalate privilege and bypass namespace isolation unexpectedly.

Upstream Commit:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=24f6008564183aa120d07c03d9289519c2fe02af

A heap-based buffer overflow flaw was found in the way the legacyparseparam function in the Filesystem Context functionality of the Linux kernel verified the supplied parameters length. An unprivileged (in case of unprivileged user namespaces enabled, otherwise needs namespaced CAPSYSADMIN privilege) local user able to open a filesystem that does not support the Filesystem Context API (and thus fallbacks to legacy handling) could use this flaw to escalate their privileges on the system.