Linux: >> Linux Kernel >> 5.4.13 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
ipv6: icmp: clear skb2->cb[] in ip6_err_gen_icmpv6_unreach()
Sashiko AI-review observed:
In ip6_err_gen_icmpv6_unreach(), the skb is an outer IPv4 ICMP error packet
where its cb contains an IPv4 inet_skb_parm. When skb is cloned into skb2
and passed to icmp6_send(), it uses IP6CB(skb2).
IP6CB interprets the IPv4 inet_skb_parm as an inet6_skb_parm. The cipso
offset in inet_skb_parm.opt directly overlaps with dsthao in inet6_skb_parm
at offset 18.
If an attacker sends a forged ICMPv4 error with a CIPSO IP option, dsthao
would be a non-zero offset. Inside icmp6_send(), mip6_addr_swap() is called
and uses ipv6_find_tlv(skb, opt->dsthao, IPV6_TLV_HAO).
This would scan the inner, attacker-controlled IPv6 packet starting at that
offset, potentially returning a fake TLV without checking if the remaining
packet length can hold the full 18-byte struct ipv6_destopt_hao.
Could mip6_addr_swap() then perform a 16-byte swap that extends past the end
of the packet data into skb_shared_info?
Should the cb array also be cleared in ip6_err_gen_icmpv6_unreach() and
ip6ip6_err() to prevent this?
This patch implements the first suggestion.
I am not sure if ip6ip6_err() needs to be changed.
A separate patch would be better anyway.
CVSS Score
9.8
EPSS Score
0.003
Published
2026-05-01
In the Linux kernel, the following vulnerability has been resolved:
netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent
ctnetlink_alloc_expect() allocates expectations from a non-zeroing
slab cache via nf_ct_expect_alloc(). When CTA_EXPECT_NAT is not
present in the netlink message, saved_addr and saved_proto are
never initialized. Stale data from a previous slab occupant can
then be dumped to userspace by ctnetlink_exp_dump_expect(), which
checks these fields to decide whether to emit CTA_EXPECT_NAT.
The safe sibling nf_ct_expect_init(), used by the packet path,
explicitly zeroes these fields.
Zero saved_addr, saved_proto and dir in the else branch, guarded
by IS_ENABLED(CONFIG_NF_NAT) since these fields only exist when
NAT is enabled.
Confirmed by priming the expect slab with NAT-bearing expectations,
freeing them, creating a new expectation without CTA_EXPECT_NAT,
and observing that the ctnetlink dump emits a spurious
CTA_EXPECT_NAT containing stale data from the prior allocation.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-01
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nf_conntrack_helper: pass helper to expect cleanup
nf_conntrack_helper_unregister() calls nf_ct_expect_iterate_destroy()
to remove expectations belonging to the helper being unregistered.
However, it passes NULL instead of the helper pointer as the data
argument, so expect_iter_me() never matches any expectation and all
of them survive the cleanup.
After unregister returns, nfnl_cthelper_del() frees the helper
object immediately. Subsequent expectation dumps or packet-driven
init_conntrack() calls then dereference the freed exp->helper,
causing a use-after-free.
Pass the actual helper pointer so expectations referencing it are
properly destroyed before the helper object is freed.
BUG: KASAN: slab-use-after-free in string+0x38f/0x430
Read of size 1 at addr ffff888003b14d20 by task poc/103
Call Trace:
string+0x38f/0x430
vsnprintf+0x3cc/0x1170
seq_printf+0x17a/0x240
exp_seq_show+0x2e5/0x560
seq_read_iter+0x419/0x1280
proc_reg_read+0x1ac/0x270
vfs_read+0x179/0x930
ksys_read+0xef/0x1c0
Freed by task 103:
The buggy address is located 32 bytes inside of
freed 192-byte region [ffff888003b14d00, ffff888003b14dc0)
CVSS Score
7.8
EPSS Score
0.001
Published
2026-05-01
In the Linux kernel, the following vulnerability has been resolved:
netfilter: x_tables: ensure names are nul-terminated
Reject names that lack a \0 character before feeding them
to functions that expect c-strings.
Fixes tag is the most recent commit that needs this change.
CVSS Score
7.1
EPSS Score
0.001
Published
2026-05-01
In the Linux kernel, the following vulnerability has been resolved:
crypto: authencesn - Do not place hiseq at end of dst for out-of-place decryption
When decrypting data that is not in-place (src != dst), there is
no need to save the high-order sequence bits in dst as it could
simply be re-copied from the source.
However, the data to be hashed need to be rearranged accordingly.
Thanks,
CVSS Score
7.8
EPSS Score
0.001
Published
2026-05-01
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: MGMT: validate LTK enc_size on load
Load Long Term Keys stores the user-provided enc_size and later uses
it to size fixed-size stack operations when replying to LE LTK
requests. An enc_size larger than the 16-byte key buffer can therefore
overflow the reply stack buffer.
Reject oversized enc_size values while validating the management LTK
record so invalid keys never reach the stored key state.
CVSS Score
7.8
EPSS Score
0.001
Published
2026-05-01
In the Linux kernel, the following vulnerability has been resolved:
net: macb: properly unregister fixed rate clocks
The additional resources allocated with clk_register_fixed_rate() need
to be released with clk_unregister_fixed_rate(), otherwise they are lost.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-01
In the Linux kernel, the following vulnerability has been resolved:
net/x25: Fix potential double free of skb
When alloc_skb fails in x25_queue_rx_frame it calls kfree_skb(skb) at
line 48 and returns 1 (error).
This error propagates back through the call chain:
x25_queue_rx_frame returns 1
|
v
x25_state3_machine receives the return value 1 and takes the else
branch at line 278, setting queued=0 and returning 0
|
v
x25_process_rx_frame returns queued=0
|
v
x25_backlog_rcv at line 452 sees queued=0 and calls kfree_skb(skb)
again
This would free the same skb twice. Looking at x25_backlog_rcv:
net/x25/x25_in.c:x25_backlog_rcv() {
...
queued = x25_process_rx_frame(sk, skb);
...
if (!queued)
kfree_skb(skb);
}
CVSS Score
9.8
EPSS Score
0.005
Published
2026-05-01
In the Linux kernel, the following vulnerability has been resolved:
ALSA: ctxfi: Check the error for index mapping
The ctxfi driver blindly assumed a proper value returned from
daio_device_index(), but it's not always true. Add a proper error
check to deal with the error from the function.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-05-01
In the Linux kernel, the following vulnerability has been resolved:
ALSA: caiaq: fix stack out-of-bounds read in init_card
The loop creates a whitespace-stripped copy of the card shortname
where `len < sizeof(card->id)` is used for the bounds check. Since
sizeof(card->id) is 16 and the local id buffer is also 16 bytes,
writing 16 non-space characters fills the entire buffer,
overwriting the terminating nullbyte.
When this non-null-terminated string is later passed to
snd_card_set_id() -> copy_valid_id_string(), the function scans
forward with `while (*nid && ...)` and reads past the end of the
stack buffer, reading the contents of the stack.
A USB device with a product name containing many non-ASCII, non-space
characters (e.g. multibyte UTF-8) will reliably trigger this as follows:
BUG: KASAN: stack-out-of-bounds in copy_valid_id_string
sound/core/init.c:696 [inline]
BUG: KASAN: stack-out-of-bounds in snd_card_set_id_no_lock+0x698/0x74c
sound/core/init.c:718
The off-by-one has been present since commit bafeee5b1f8d ("ALSA:
snd_usb_caiaq: give better shortname") from June 2009 (v2.6.31-rc1),
which first introduced this whitespace-stripping loop. The original
code never accounted for the null terminator when bounding the copy.
Fix this by changing the loop bound to `sizeof(card->id) - 1`,
ensuring at least one byte remains as the null terminator.
CVSS Score
7.1
EPSS Score
0.001
Published
2026-05-01