Linux: >> Linux Kernel >> 6.12.33 Security Vulnerabilities
In the Linux kernel, the following vulnerability has been resolved:
ipv6: mcast: Fix use-after-free when processing MLD queries
When processing an MLD query, a pointer to the multicast group address
is retrieved when initially parsing the packet. This pointer is later
dereferenced without being reloaded despite the fact that the skb header
might have been reallocated following the pskb_may_pull() calls, leading
to a use-after-free [1].
Fix by copying the multicast group address when the packet is initially
parsed.
[1]
BUG: KASAN: slab-use-after-free in __mld_query_work (net/ipv6/mcast.c:1512)
Read of size 8 at addr ffff8881154b8e90 by task kworker/4:1/118
Workqueue: mld mld_query_work
Call Trace:
<TASK>
dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)
print_address_description.constprop.0 (mm/kasan/report.c:378)
print_report (mm/kasan/report.c:482)
kasan_report (mm/kasan/report.c:595)
__mld_query_work (net/ipv6/mcast.c:1512)
mld_query_work (net/ipv6/mcast.c:1563)
process_one_work (kernel/workqueue.c:3314)
worker_thread (kernel/workqueue.c:3397 kernel/workqueue.c:3478)
kthread (kernel/kthread.c:436)
ret_from_fork (arch/x86/kernel/process.c:158)
ret_from_fork_asm (arch/x86/entry/entry_64.S:245)
</TASK>
[...]
Freed by task 118:
kasan_save_stack (mm/kasan/common.c:57)
kasan_save_track (mm/kasan/common.c:78)
kasan_save_free_info (mm/kasan/generic.c:584)
__kasan_slab_free (mm/kasan/common.c:253 mm/kasan/common.c:285)
kfree (./include/linux/kasan.h:235 mm/slub.c:2689 mm/slub.c:6251 mm/slub.c:6566)
pskb_expand_head (net/core/skbuff.c:2335)
__pskb_pull_tail (net/core/skbuff.c:2878 (discriminator 4))
__mld_query_work (net/ipv6/mcast.c:1495 (discriminator 1))
mld_query_work (net/ipv6/mcast.c:1563)
process_one_work (kernel/workqueue.c:3314)
worker_thread (kernel/workqueue.c:3397 kernel/workqueue.c:3478)
kthread (kernel/kthread.c:436)
ret_from_fork (arch/x86/kernel/process.c:158)
ret_from_fork_asm (arch/x86/entry/entry_64.S:245)
CVSS Score
8.8
EPSS Score
0.003
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
KVM: arm64: Take the SRCU lock for page table walks in fault injection and AT emulation
walk_s1() and kvm_walk_nested_s2() expect to be called while holding
kvm->srcu to guard against memslot changes. While this is generally
the case, __kvm_at_s12() and __kvm_find_s1_desc_level() call into the
respective walkers without taking kvm->srcu.
Fix by acquiring kvm->srcu prior to the table walk in both instances.
CVSS Score
8.8
EPSS Score
0.001
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
devlink: Release nested relation on devlink free
devlink relation state is normally released from devl_unregister(), which
calls devlink_rel_put(). This misses devlink instances that get a nested
relation before registration and then fail probe before devl_register() is
reached.
That flow can happen for SFs. The child devlink gets linked to its
parent before registration, then a later probe error calls devlink_free()
directly. Since the instance was never registered, devl_unregister() is not
called and devlink->rel is leaked.
Release any pending relation from devlink_free() as well. The registered
path is unchanged because devl_unregister() already clears devlink->rel
before devlink_free() runs.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
l2tp: pppol2tp: hold reference to session in pppol2tp_ioctl()
pppol2tp_ioctl() read sock->sk->sk_user_data directly without any
locks or reference counting. If a controllable sleep was induced during
copy_from_user() (e.g. via a userfaultfd page fault sleep), a concurrent
socket close could trigger pppol2tp_session_close() asynchronously. This
frees the l2tp_session structure via the l2tp_session_del_work workqueue.
Upon resuming, the ioctl thread dereferences the stale session pointer,
resulting in a Use-After-Free (UAF).
Fix this by securely fetching the session reference using the RCU-safe,
refcounted helper pppol2tp_sock_to_session(sk) on entry. This locks the
session's refcount across the sleep. We structured the function to exit
via standard err breaks, guaranteeing that l2tp_session_put() is cleanly
called on all return paths to drop the reference.
To preserve existing behavior we validate the session and its magic
signature only for the specific L2TP commands that require it. This
ensures that generic/unknown ioctls called on an unconnected socket
still return -ENOIOCTLCMD and correctly fall back to generic handlers
(e.g. in sock_do_ioctl()).
CVSS Score
7.8
EPSS Score
0.001
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
6lowpan: fix off-by-one in multicast context address compression
The second memcpy in lowpan_iphc_mcast_ctx_addr_compress() uses
&data[1] as destination and &ipaddr->s6_addr[11] as source, but
both should be offset by one: &data[2] and &ipaddr->s6_addr[12]
respectively.
This off-by-one has two consequences:
1. data[1] is overwritten with s6_addr[11], corrupting the RIID
field in the compressed multicast address
2. data[5] is never written, so uninitialized kernel stack memory
is transmitted over the network via lowpan_push_hc_data(),
leaking kernel stack contents
The correct inline data layout must match what the decompression
function lowpan_uncompress_multicast_ctx_daddr() expects:
data[0..1] = s6_addr[1..2] (flags/scope + RIID)
data[2..5] = s6_addr[12..15] (group ID)
Also zero-initialize the data array as a defensive measure against
similar bugs in the future.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
net/sched: act_api: use RCU with deferred freeing for action lifecycle
When NEWTFILTER and DELFILTER are run concurrently it is possible to create a
race with an associated action.
Let's illustrate with CPU0 running NEWTFILTER and CPU1 running DELFILTER:
0: mutex_lock() <-- holds the idr lock
0: rcu_read_lock()
0: p = idr_find(idr, index) <-- action p is valid (RCU protects IDR)
0: mutex_unlock() <-- releases the idr lock
1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held
1: idr_remove(idr, index) <-- Action removed from IDR
1: mutex_unlock() <-- mutex released allowing us to delete the action
1: tcf_action_cleanup(p); kfree(p) <-- Kfrees p immediately, no deferral
0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- ouch, UAF p points to freed memory
This patch fixes the race condition between NEWTFILTER and DELFILTER by
adding struct rcu_head to tc_action used in the deferral and introducing a
call_rcu() in the delete path to defer the final kfree().
Note: this is a revert of commit d7fb60b9cafb ("net_sched: get rid of tcfa_rcu")
but also modernization/simplification to directly use kfree_rcu().
Let's illustrate the new restored code path:
0: rcu_read_lock()
1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held
1: idr_remove(idr, index)
1: mutex_unlock()
1: call_rcu(&p->tcfa_rcu, tcf_action_rcu_free) <-- defer kfree after grace period
0: p = idr_find(idr, index)
0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- fails, refcnt already 0
1: rcu_read_unlock() <-- release so freeing can run after grace period
After CPU1 calls idr_remove(), the object is no longer reachable through the IDR.
CPU0's subsequent idr_find() will return NULL, and even if it still held a
stale pointer, the immediate kfree() is now deferred until after the RCU grace
period, so no UAF can occur.
CVSS Score
7.8
EPSS Score
0.001
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
netfilter: bridge: make ebt_snat ARP rewrite writable
The ebtables SNAT target keeps the Ethernet source address rewrite
behind skb_ensure_writable(skb, 0). This is intentional: at the bridge
ebtables hooks the Ethernet header is addressed through
skb_mac_header()/eth_hdr(), while skb->data points at the Ethernet
payload. Asking skb_ensure_writable() for ETH_HLEN bytes would check
the payload, not the Ethernet header, and would reintroduce the small
packet regression fixed by commit 63137bc5882a.
However, the optional ARP sender hardware address rewrite is different.
It writes through skb_store_bits() at an offset relative to skb->data:
skb_store_bits(skb, sizeof(struct arphdr), info->mac, ETH_ALEN)
skb_header_pointer() only safely reads the ARP header; it does not make
the later sender hardware address range writable. If that range is
still held in a nonlinear skb fragment backed by a splice-imported file
page, skb_store_bits() maps the frag page and copies the new MAC address
directly into it.
Ensure the ARP SHA range is writable before reading the ARP header and
before calling skb_store_bits().
CVSS Score
8.8
EPSS Score
0.001
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nft_ct: bail out on template ct in get eval
I noticed this issue while looking at a historic syzbot report [1].
A rule like the one below is enough to trigger the bug:
table ip t {
chain pre {
type filter hook prerouting priority raw;
ct zone set 1
ct original saddr 1.2.3.4 accept
}
}
The first expression attaches a per-cpu template ct via
nft_ct_set_zone_eval() (nf_ct_tmpl_alloc -> kzalloc, tuple is all
zero, nf_ct_l3num(ct) == 0). The next expression then calls
nft_ct_get_eval() on the same skb, treats the template as a real ct
and hits the 16-byte memcpy path. With dreg at NFT_REG32_15 this
overflows past struct nft_regs on the kernel stack; with smaller
dreg values it silently clobbers adjacent registers.
Reject template ct at the eval entry and in nft_ct_get_fast_eval(),
mirroring the check nft_ct_set_eval() already has. Additionally,
bound the address copy in NFT_CT_SRC / NFT_CT_DST by priv->len
instead of by nf_ct_l3num(ct): nf_ct_get_tuple() zeroes the tuple
before pkt_to_tuple() fills in only the protocol-relevant leading
bytes, so the trailing bytes of tuple->{src,dst}.u3.all are
well-defined zero. priv->len is validated at rule load, so the
copy size is now bounded by the destination register rather than
by an untrusted field on the conntrack.
[1]: https://syzkaller.appspot.com/bug?id=389cf09cb72926114fce90dc85a2c3231dcb647c
CVSS Score
7.8
EPSS Score
0.001
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
netfilter: conntrack_irc: fix possible out-of-bounds read
When parsing fails after we've matched the command string we
should bail out instead of trying to match a different command.
This helper should be deprecated, given prevalence of TLS I doubt it has
any relevance in 2026.
CVSS Score
8.2
EPSS Score
0.004
Published
2026-06-25
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: ISO: Fix not releasing hdev reference on iso_conn_big_sync
hci_get_route() returns a reference-counted hci_dev pointer via
hci_dev_hold(). The function exits normally or with an error without ever
releasing it.
CVSS Score
5.5
EPSS Score
0.001
Published
2026-06-25