CVE-2026-53275

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)