In FreeBSD 15.0, the kernel structure used to represent user credentials changed: previously the primary group ID was stored in the first element of the array containing the list of supplementary group IDs, whereas now the primary group ID is stored in a dedicated field. This change was largely internal to the kernel and not user-visible.

One function, groupisprimary(), was not properly updated as a part of this transition. This function is used by macdo to determine the primary group ID of the credential after applying a transition rule, used when the rule target does not explicitly specify a group.

As a result, with certain macdo rules, it is possible for a credential switch to incorrectly set the primary group ID to the ID stored in the first element of the original credential's supplementary group array.

If the list of supplementary groups is empty, this value will be 0, corresponding to the "wheel" group. For example, a rule such as "uid=1001>uid=1002" can be abused to set the primary group ID to 0 even if the process did not originally belong to group 0.

Certain macdo rules can be abused to set a process' group ID to 0. Note however, that the rule must apply to the caller in order for the bug to be triggered, e.g., given the ruleset "uid=1001>uid=1002", the user must have user ID 1001 in order to trigger the bug.

Further, logged-in users will in general have a non-empty supplementary group list, in which case the bug can at worst be used to set the credential's first supplementary group ID as its primary group ID. Processes must explicitly remove themselves from all supplementary groups, using the privileged setgroups(2) system call, in order to exploit the bug to set 0 as the primary group ID.

Since membership in group 0 is often used to enable controlled privilege escalation, the bug might be further exploitable to obtain root privileges, depending on the system configuration. For instance, a ruleset such as the following could be exploited by a process running as user 1001 and with an empty supplementary group list: "uid=1001>uid=1002;gid=0>uid=0".

When a process calls execve(2) to execute a setuid or setgid image, hwpmc(4) is supposed to detach PMCs owned by unprivileged processes. An inverted check meant that this scenario was not handled properly.

An unprivileged local user who has attached PMCs to a process can continue monitoring it after the process executes a setuid or setgid binary, contrary to the intended policy.

The ELF core dump code counted the number of dumpable VM map entries, allocated a buffer for the corresponding program headers, then iterated over the map a second time to populate them. A process sharing the address space via rfork(2) can mutate the map between the two passes, causing the second pass to write program headers past the end of the buffer.

An unprivileged local user sharing an address space with a process that dumps core can trigger an out-of-bounds write on the kernel heap, potentially leading to privilege escalation.

The GETALL and SETALL commands in semctl(2) recorded the number of semaphores in the target set, dropped the lock protecting the set, allocated a buffer sized for that count, and reacquired the lock. A sequence-number check was used to verify that the set had not been replaced in the interim, but the sequence number wraps after 0x8000 create/destroy cycles. By rapidly destroying and recreating semaphore sets at the same index, another process can cause the sequence number to wrap, allowing a set with a different number of semaphores to pass validation. The subsequent copy then reads or writes past the end of the allocated buffer.

An unprivileged local user can trigger out-of-bounds reads and writes on kernel heap memory, potentially leading to privilege escalation.

As an inadvertent side effect of an unrelated code change, PRIVKTRACE was always denied to a jailed root user. Tracing configured by a jailed root user was therefore not flagged as privileged.

An unprivileged user in a jail that has permission to debug the target process can modify the jailed root user's ktrace(2) flags, or disable tracing outright. A jailed root user therefore cannot reliably trace unprivileged processes.

After dispatching a decrypt operation to OCF and receiving the result, the wg(4) driver failed to check whether the MAC verification step succeeded. The driver thus silently accepted packets with an invalid Poly1305 authentication tag.

A remote attacker who can send UDP packets to a WireGuard endpoint, and who can guess the bounds of the receiver's replay window, can inject forged or modified transport data packets into the tunnel.

A remote attacker who can intercept WireGuard packets bound for a FreeBSD host can modify the ciphertext and authenticated data without detection by the receiver.

To retrieve the previous timer value, the kernel calls realtimergettime(), which obtains the current time for the timer's clock. For a timer using CLOCKTAI this can fail when no TAI offset has been configured, but the error return was not checked, so the uninitialized output buffer was copied to userspace.

An unprivileged local user can obtain uninitialized kernel stack memory by creating a POSIX timer with CLOCKTAI and calling timersettime(2), potentially disclosing sensitive kernel data.

While the kernel was copying knotes during fork, a knote with a timer-based filter could fire and be enqueued on the kqueue's active list before the copy was complete. The copy routine did not account for this and could enqueue the new knote a second time, corrupting the active list. In addition, the copy routine did not hold the appropriate locks while reading knote state, allowing further races.

An unprivileged local user can trigger a use-after-free in the kernel, potentially leading to privilege escalation.

The ISO-2022 encoding module used a stack buffer sized to MBLENMAX (6 bytes) for intermediate character output. Some ISO-2022 variants can require up to 10 bytes per character, in which case conversions can trigger a stack buffer overflow of up to four bytes.

An application that uses iconv(3) to convert untrusted input to or from one of the affected encodings may be vulnerable to buffer overflows if it uses one of the affected encoding modules.

Several encoding modules, including HZ, UTF-7, VIQR, and ZW, did not properly check the size of the caller-supplied output buffer before writing converted characters.

An application that uses iconv(3) to convert untrusted input to or from one of the affected encodings may be vulnerable to buffer overflows if it uses one of the affected encoding modules.

The compat32 kevent() handler translates a 64-bit kevent struct into a stack- declared 32-bit struct. It did not first zero the stack struct.

An unprivileged user may observe a small amount of uninitialized kernel stack data, which may contain sensitive information.

The Linux waitid() implementation translates a FreeBSD siginfot struct into a stack-declared Linux siginfot. It did not first zero the stack struct.

An unprivileged user may observe 104 bytes of uninitialized kernel stack data, which may contain sensitive information.

When building the iovec array for a received TLS 1.2 CBC record, ktlsocftlscbcdecrypt() incremented the iovec index for every mbuf in the chain, including mbufs that were skipped because they contained only TLS header bytes. This left uninitialized entries in the iovec array. The iovec array was allocated without zeroing.

A remote TLS peer can cause the kernel to read from uninitialized iovec entries during HMAC computation, resulting in a kernel panic. The peer must be able to control TCP segmentation such that the first mbuf of a CBC record contains only the 5-byte TLS record header.

When auditing a system call executed via ptrace(PTSCREMOTE), the kernel passed the return value of an internal setup function to AUDITSYSCALLEXIT() rather than the actual result of the executed system call. As a result, committed audit records for system calls which returned an error do not reflect the true outcome of the operation. That is, they indicate that the operation succeeded when it in fact failed.

Audit records for system calls executed via ptrace(PTSCREMOTE) may show an incorrect error status. An attacker with the ability to debug a process could use this to produce misleading audit trails, potentially undermining audit-based Intrusion Detection Systems (IDS).

Certain system calls, such open(2) with the OTRUNC flag set, and fspacectl(2), could incorrectly free memory in largepage objects. These operations are not permitted on largepage objects, but the implementation did not verify this.

An unprivileged local user can abuse the bug to access freed kernel memory. This can be exploited to escalate privileges.

Pages belonging to largepage shared memory objects were not explicitly wired. When sendfile(2) transmitted such an object with the SFNOCACHE flag, it freed the underlying pages after transmission even though existing mappings still referred to them.

An unprivileged local user can abuse the bug to access freed kernel memory. This can be exploited to escalate privileges.

The RACK setsockopt(2) handler drops the connection lock in order to copy option data from userspace, then reacquires the lock. After reacquiring, it verifies that the TCP stack had not been switched away, but did not reload its pointer to the stack's per-connection control block. If userspace switches stacks twice during this window, the check will succeed but the saved pointer will refer to freed memory.

The bug may be exploitable by an unprivileged local user to escalate privileges.

The kernel function that implements unlinkat(2) and funlinkat(2) validated the ATRESOLVEBENEATH flag but failed to pass it through to the underlying path lookup. The flag was silently dropped, so path resolution was not actually restricted.

A process that uses ATRESOLVEBENEATH with unlinkat(2) or funlinkat(2) to confine path resolution can in fact resolve paths above the starting directory. A caller relying on this flag for path containment may delete files outside the intended directory tree.

The RTSP handler in libalias rewrote outgoing packets into a fixed-length stack buffer without checking whether the rewritten data fit in the buffer, or whether the result fit back in the original packet.

A host sending crafted RTSP traffic from inside a NAT gateway using libalias can overflow a stack buffer, potentially achieving remote code execution in the kernel (when using ipfw(4) NAT) or in the natd(8) process (which generally runs as the root user).

The ZFSIOCSETPROP ioctl, used by zfs-set(8), incorrectly validated the calling user such that an unprivileged user is able to set metadata on a dataset indicating that the dataset has received properties from a zfs-recv(8) stream.

Any local user can set the internal ZFS metadata flag "$hasrecvd" on datasets via ZFSIOCSETPROP.

The ZFSIOCRECVNEW ioctl, in the heal receive path, similarly truncated a 64-bit payload size to a 32-bit integer for allocation, then used the original 64-bit size as the length for a byteswap operation.

A local user with the "receive" delegated ZFS permission can trigger kernel memory corruption via ZFSIOCRECVNEW by sending a crafted receive stream in heal mode.

The ZFSIOCUSERSPACEMANY ioctl, used by zfs-userspace(8), truncated a 64-bit output buffer size to a 32-bit integer for the kernel allocation, but used the original 64-bit size as the buffer limit when writing records.

A local user with the "userused" delegated ZFS permission can trigger a kernel heap overflow via the ZFSIOCUSERSPACEMANY ioctl, potentially escalating privileges.

During execve(2) of a SUID binary, the new virtual address space is installed before the process credentials are updated. During this window, a process running as the same user can access the target process's memory via procfs or linprocfs, because the kernel's debugging permission check still saw the original credentials.

An unprivileged local user can exploit this race to modify the address space of a SUID binary before its credentials are elevated, potentially gaining full control of the affected system.

When the JAILATDESC flag is specified, kernjailset() and kernjailget() released the reference to the caller's current prison before looking up the jail descriptor. If the descriptor lookup failed, error-handling paths released the same reference a second time.

An unprivileged local user can trigger a prison reference count underflow, which may cause the prison structure to be freed while still in use. When this is done on the jail host, the bug will generally result in an immediate panic. However, if the user is running in a jail, then it may be possible to exploit the bug to elevate privileges.

When msync(MSINVALIDATE) is called on a mapping of an unmanaged device object, the physical pages in the mapping range are marked invalid but remain in the pager's page list. A subsequent page fault will cause the fault handler to re-insert the page into the object's list. This corrupts the list, and on object destruction the page is freed twice.

An unprivileged local user with access to a device that provides memory-mapped I/O can trigger a use-after-free in the kernel, though this is limited to a pool of objects ("fictitious pages") that are never recycled for a different purpose. It may be possible to exploit this to escalate privileges.

The CONSHISTORY ioctl handler did not adequately validate the requested history size. A large value caused an integer overflow in the buffer size calculation, resulting in a heap allocation smaller than expected. Subsequent initialization of the buffer wrote beyond the end of the allocation.

An unprivileged local user with access to a vt(4) device can trigger an out-of-bounds write in the kernel, potentially escalating privileges.

The ELF image activator cleared per-process ASLR preference flags for setuid binaries after the code that computes the PIE base address, rather than before. As a result, a user-requested ASLR disable was still in effect at the point where the base address was chosen.

An unprivileged local user can disable ASLR for a setuid PIE binary by calling procctl(2) before execve(2). This makes exploitation of any separate memory corruption vulnerability in that binary significantly easier.

The Linuxulator determined whether a binary was set-user-ID or set-group-ID by checking the PSUGID process flag. During execve(2), this flag is not yet set at the point where the auxiliary vector is constructed, so ATSECURE was incorrectly set to zero for set-user-ID and set-group-ID executables.

An unprivileged local user can inject a shared library via LDPRELOAD into a set-user-ID or set-group-ID Linux binary, gaining the privileges of that binary.

The kernel handler for IPV6MSFILTER dropped a serializing lock in order to copy the source-filter list from userspace, then reacquired the lock. During this window another thread could free the multicast filter structure, leaving the handler with a stale pointer to freed memory.

An unprivileged local user can exploit this use-after-free to escalate privileges.

sigqueue(2) was marked as permitted in capability mode with the introduction of Capsicum in 2011, but the implementation of kernsigqueue did not include a capability mode check restricting signal delivery to the calling process's own PID.

A process in capability mode can use sigqueue(2) to send signals to any process it could signal following standard Unix permissions, bypassing the Capsicum sandbox restriction. A compromised sandboxed process could interfere with other processes, for example by sending SIGKILL or SIGSTOP. This could be any process running as the same user, or any process, for a superuser sandboxed process.