Linux: >> Linux Kernel >> 6.18.8 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
phy: freescale: imx8qm-hsio: fix NULL pointer dereference
During the probe the refclk_pad pointer is set to NULL if the
'fsl,refclk-pad-mode' property is not defined in the devicetree node. But
in imx_hsio_configure_clk_pad() this pointer is unconditionally used which
could result in a NULL pointer dereference. So check the pointer before to
use it.
CVSS Score
5.5
EPSS Score
0.002
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nfnetlink_queue: do shared-unconfirmed check before segmentation
Ulrich reports a regression with nfqueue:
If an application did not set the 'F_GSO' capability flag and a gso
packet with an unconfirmed nf_conn entry is received all packets are
now dropped instead of queued, because the check happens after
skb_gso_segment(). In that case, we did have exclusive ownership
of the skb and its associated conntrack entry. The elevated use
count is due to skb_clone happening via skb_gso_segment().
Move the check so that its peformed vs. the aggregated packet.
Then, annotate the individual segments except the first one so we
can do a 2nd check at reinject time.
For the normal case, where userspace does in-order reinjects, this avoids
packet drops: first reinjected segment continues traversal and confirms
entry, remaining segments observe the confirmed entry.
While at it, simplify nf_ct_drop_unconfirmed(): We only care about
unconfirmed entries with a refcnt > 1, there is no need to special-case
dying entries.
This only happens with UDP. With TCP, the only unconfirmed packet will
be the TCP SYN, those aren't aggregated by GRO.
Next patch adds a udpgro test case to cover this scenario.
CVSS Score
7.5
EPSS Score
0.006
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nf_conncount: increase the connection clean up limit to 64
After the optimization to only perform one GC per jiffy, a new problem
was introduced. If more than 8 new connections are tracked per jiffy the
list won't be cleaned up fast enough possibly reaching the limit
wrongly.
In order to prevent this issue, only skip the GC if it was already
triggered during the same jiffy and the increment is lower than the
clean up limit. In addition, increase the clean up limit to 64
connections to avoid triggering GC too often and do more effective GCs.
This has been tested using a HTTP server and several
performance tools while having nft_connlimit/xt_connlimit or OVS limit
configured.
Output of slowhttptest + OVS limit at 52000 connections:
slow HTTP test status on 340th second:
initializing: 0
pending: 432
connected: 51998
error: 0
closed: 0
service available: YES
CVSS Score
7.5
EPSS Score
0.007
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
gfs2: Fix slab-use-after-free in qd_put
Commit a475c5dd16e5 ("gfs2: Free quota data objects synchronously")
started freeing quota data objects during filesystem shutdown instead of
putting them back onto the LRU list, but it failed to remove these
objects from the LRU list, causing LRU list corruption. This caused
use-after-free when the shrinker (gfs2_qd_shrink_scan) tried to access
already-freed objects on the LRU list.
Fix this by removing qd objects from the LRU list before freeing them in
qd_put().
Initial fix from Deepanshu Kartikey <kartikey406@gmail.com>.
CVSS Score
7.8
EPSS Score
0.002
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
iommu/vt-d: Flush cache for PASID table before using it
When writing the address of a freshly allocated zero-initialized PASID
table to a PASID directory entry, do that after the CPU cache flush for
this PASID table, not before it, to avoid the time window when this
PASID table may be already used by non-coherent IOMMU hardware while
its contents in RAM is still some random old data, not zero-initialized.
CVSS Score
7.8
EPSS Score
0.001
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
i3c: dw: Fix memory leak in dw_i3c_master_i2c_xfers()
The dw_i3c_master_i2c_xfers() function allocates memory for the xfer
structure using dw_i3c_master_alloc_xfer(). If pm_runtime_resume_and_get()
fails, the function returns without freeing the allocated xfer, resulting
in a memory leak.
Add a dw_i3c_master_free_xfer() call to the error path to ensure the
allocated memory is properly freed.
Compile tested only. Issue found using a prototype static analysis tool
and code review.
CVSS Score
5.5
EPSS Score
0.002
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
fs/ntfs3: prevent infinite loops caused by the next valid being the same
When processing valid within the range [valid : pos), if valid cannot
be retrieved correctly, for example, if the retrieved valid value is
always the same, this can trigger a potential infinite loop, similar
to the hung problem reported by syzbot [1].
Adding a check for the valid value within the loop body, and terminating
the loop and returning -EINVAL if the value is the same as the current
value, can prevent this.
[1]
INFO: task syz.4.21:6056 blocked for more than 143 seconds.
Call Trace:
rwbase_write_lock+0x14f/0x750 kernel/locking/rwbase_rt.c:244
inode_lock include/linux/fs.h:1027 [inline]
ntfs_file_write_iter+0xe6/0x870 fs/ntfs3/file.c:1284
CVSS Score
5.5
EPSS Score
0.002
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
mctp i2c: initialise event handler read bytes
Set a 0xff value for i2c reads of an mctp-i2c device. Otherwise reads
will return "val" from the i2c bus driver. For i2c-aspeed and
i2c-npcm7xx that is a stack uninitialised u8.
Tested with "i2ctransfer -y 1 r10@0x34" where 0x34 is a mctp-i2c
instance, now it returns all 0xff.
CVSS Score
5.5
EPSS Score
0.002
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
serial: caif: fix use-after-free in caif_serial ldisc_close()
There is a use-after-free bug in caif_serial where handle_tx() may
access ser->tty after the tty has been freed.
The race condition occurs between ldisc_close() and packet transmission:
CPU 0 (close) CPU 1 (xmit)
------------- ------------
ldisc_close()
tty_kref_put(ser->tty)
[tty may be freed here]
<-- race window -->
caif_xmit()
handle_tx()
tty = ser->tty // dangling ptr
tty->ops->write() // UAF!
schedule_work()
ser_release()
unregister_netdevice()
The root cause is that tty_kref_put() is called in ldisc_close() while
the network device is still active and can receive packets.
Since ser and tty have a 1:1 binding relationship with consistent
lifecycles (ser is allocated in ldisc_open and freed in ser_release
via unregister_netdevice, and each ser binds exactly one tty), we can
safely defer the tty reference release to ser_release() where the
network device is unregistered.
Fix this by moving tty_kref_put() from ldisc_close() to ser_release(),
after unregister_netdevice(). This ensures the tty reference is held
as long as the network device exists, preventing the UAF.
Note: We save ser->tty before unregister_netdevice() because ser is
embedded in netdev's private data and will be freed along with netdev
(needs_free_netdev = true).
How to reproduce: Add mdelay(500) at the beginning of ldisc_close()
to widen the race window, then run the reproducer program [1].
Note: There is a separate deadloop issue in handle_tx() when using
PORT_UNKNOWN serial ports (e.g., /dev/ttyS3 in QEMU without proper
serial backend). This deadloop exists even without this patch,
and is likely caused by inconsistency between uart_write_room() and
uart_write() in serial core. It has been addressed in a separate
patch [2].
KASAN report:
==================================================================
BUG: KASAN: slab-use-after-free in handle_tx+0x5d1/0x620
Read of size 1 at addr ffff8881131e1490 by task caif_uaf_trigge/9929
Call Trace:
<TASK>
dump_stack_lvl+0x10e/0x1f0
print_report+0xd0/0x630
kasan_report+0xe4/0x120
handle_tx+0x5d1/0x620
dev_hard_start_xmit+0x9d/0x6c0
__dev_queue_xmit+0x6e2/0x4410
packet_xmit+0x243/0x360
packet_sendmsg+0x26cf/0x5500
__sys_sendto+0x4a3/0x520
__x64_sys_sendto+0xe0/0x1c0
do_syscall_64+0xc9/0xf80
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f615df2c0d7
Allocated by task 9930:
Freed by task 64:
Last potentially related work creation:
The buggy address belongs to the object at ffff8881131e1000
which belongs to the cache kmalloc-cg-2k of size 2048
The buggy address is located 1168 bytes inside of
freed 2048-byte region [ffff8881131e1000, ffff8881131e1800)
The buggy address belongs to the physical page:
page_owner tracks the page as allocated
page last free pid 9778 tgid 9778 stack trace:
Memory state around the buggy address:
ffff8881131e1380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881131e1400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881131e1480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881131e1500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881131e1580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
[1]: https://gist.github.com/mrpre/f683f244544f7b11e7fa87df9e6c2eeb
[2]: https://lore.kernel.org/linux-serial/20260204074327.226165-1-jiayuan.chen@linux.dev/T/#u
CVSS Score
7.8
EPSS Score
0.002
Published
2026-05-27
In the Linux kernel, the following vulnerability has been resolved:
efi: Fix reservation of unaccepted memory table
The reserve_unaccepted() function incorrectly calculates the size of the
memblock reservation for the unaccepted memory table. It aligns the
size of the table, but fails to account for cases where the table's
starting physical address (efi.unaccepted) is not page-aligned.
If the table starts at an offset within a page and its end crosses into
a subsequent page that the aligned size does not cover, the end of the
table will not be reserved. This can lead to the table being overwritten
or inaccessible, causing a kernel panic in accept_memory().
This issue was observed when starting Intel TDX VMs with specific memory
sizes (e.g., > 64GB).
Fix this by calculating the end address first (including the unaligned
start) and then aligning it up, ensuring the entire range is covered
by the reservation.
CVSS Score
7.1
EPSS Score
0.002
Published
2026-05-27