Description
In the Linux kernel, the following vulnerability has been resolved:

xfrm: reject optional IPTFS templates in outbound policies

syzbot reported a stack-out-of-bounds read in xfrm_state_find()
which flows from xfrm_tmpl_resolve_one().

Commit 3d776e31c841 ("xfrm: Reject optional tunnel/BEET mode
templates in outbound policies") disallowed optional tunnel and
BEET in outbound policies to prevent this. Later when IPTFS
added, it was not covered by that fix and can still trigger
the out-of-bounds read;

Extend the check to disallow optional IPTFS in outbound policies
as well. IPTFS should be identical to tunnel mode.
IN and FWD policies are not affected: xfrm_tmpl_resolve_one()
is only reachable via the outbound path.

Reproducer, before:

ip link add dummy0 type dummy
ip link set dummy0 up
ip addr add 10.1.1.1/24 dev dummy0
ip xfrm policy add src 10.1.1.1/32 dst 10.1.1.2/32 dir out tmpl
src fc00::dead:1 dst fc00::dead:2 proto esp reqid 1 mode iptfs
level use tmpl src fc00::dead:1 dst fc00::dead:2 proto esp reqid
2 mode transport
ping -W 1 -c 1 10.1.1.2
PING 10.1.1.2 (10.1.1.2) 56(84) bytes of data.

[ 64.168420] ==================================================================
[ 64.169977] BUG: KASAN: stack-out-of-bounds in __xfrm6_addr_hash+0x11e/0x170
[ 64.169977] Read of size 4 at addr ffff88800e1ffd20 by task ping/2844

[ 64.169977] CPU: 2 UID: 0 PID: 2844 Comm: ping Not tainted 7.1.0-rc7-00180-geb23b588430a #98 PREEMPT(full)
[ 64.169977] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 64.169977] Call Trace:
[ 64.169977] <TASK>
[ 64.169977] dump_stack_lvl+0x47/0x70
[ 64.169977] ? __xfrm6_addr_hash+0x11e/0x170
[ 64.169977] print_report+0x152/0x4b0
[ 64.169977] ? ksys_mmap_pgoff+0x6d/0xa0
[ 64.169977] ? entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 64.169977] ? rcu_read_unlock_sched+0xa/0x20
[ 64.169977] ? __virt_addr_valid+0x21b/0x230
[ 64.169977] ? __xfrm6_addr_hash+0x11e/0x170
[ 64.169977] kasan_report+0xa8/0xd0
[ 64.169977] ? __xfrm6_addr_hash+0x11e/0x170
[ 64.169977] __xfrm6_addr_hash+0x11e/0x170
[ 64.169977] __xfrm_dst_hash+0x24/0xc0
[ 64.169977] xfrm_state_find+0xa2d/0x2f90
[ 64.169977] ? __pfx_xfrm_state_find+0x10/0x10
[ 64.169977] ? __pfx_ftrace_graph_ret_addr+0x10/0x10
[ 64.169977] ? __pfx_ftrace_graph_ret_addr+0x10/0x10
[ 64.169977] xfrm_tmpl_resolve_one+0x210/0x570
[ 64.169977] ? __pfx_xfrm_tmpl_resolve_one+0x10/0x10
[ 64.169977] ? __pfx_stack_trace_consume_entry+0x10/0x10
[ 64.169977] ? kernel_text_address+0x5b/0x80
[ 64.169977] ? __kernel_text_address+0xe/0x30
[ 64.169977] ? unwind_get_return_address+0x5e/0x90
[ 64.169977] ? arch_stack_walk+0x8c/0xe0
[ 64.169977] xfrm_tmpl_resolve+0x130/0x200
[ 64.169977] ? __pfx_xfrm_tmpl_resolve+0x10/0x10
[ 64.169977] ? __pfx_xfrm_policy_inexact_lookup_rcu+0x10/0x10
[ 64.169977] ? __refcount_add_not_zero.constprop.0+0xb2/0x110
[ 64.169977] ? __pfx___refcount_add_not_zero.constprop.0+0x10/0x10
[ 64.169977] xfrm_resolve_and_create_bundle+0xd5/0x310
[ 64.169977] ? __pfx_xfrm_resolve_and_create_bundle+0x10/0x10
[ 64.169977] ? __pfx_xfrm_policy_lookup_bytype+0x10/0x10
[ 64.169977] ? __pfx_xfrm_policy_lookup_bytype+0x10/0x10
[ 64.169977] xfrm_lookup_with_ifid+0x3d8/0xb80
[ 64.169977] ? __pfx_xfrm_lookup_with_ifid+0x10/0x10
[ 64.169977] ? ip_route_output_key_hash+0xc6/0x110
[ 64.169977] ? kasan_save_track+0x10/0x30
[ 64.169977] xfrm_lookup_route+0x18/0xe0
[ 64.169977] ip4_datagram_release_cb+0x4c9/0x530
[ 64.169977] ? __pfx_ip4_datagram_release_cb+0x10/0x10
[ 64.169977] ? do_raw_spin_lock+0x71/0xc0
[ 64.169977] ? __pfx_do_raw_spin_lock+0x10/0x10
[ 64.169977] release_sock+0xb0/0x170
[ 64.169977] udp_connect+0x43/0x50
[ 64.169977] __sys_connect+0xa6/0x100
[ 64.169977] ? alloc_fd+0x2e9/0x300
[ 64.169977] ? __pfx___sys_connect+0x10/0x10
[ 64.169977] ? preempt_latency
---truncated---
Published: 2026-08-10
Score: n/a
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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Remediation

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History

Mon, 10 Aug 2026 16:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-125

Mon, 10 Aug 2026 12:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: xfrm: reject optional IPTFS templates in outbound policies syzbot reported a stack-out-of-bounds read in xfrm_state_find() which flows from xfrm_tmpl_resolve_one(). Commit 3d776e31c841 ("xfrm: Reject optional tunnel/BEET mode templates in outbound policies") disallowed optional tunnel and BEET in outbound policies to prevent this. Later when IPTFS added, it was not covered by that fix and can still trigger the out-of-bounds read; Extend the check to disallow optional IPTFS in outbound policies as well. IPTFS should be identical to tunnel mode. IN and FWD policies are not affected: xfrm_tmpl_resolve_one() is only reachable via the outbound path. Reproducer, before: ip link add dummy0 type dummy ip link set dummy0 up ip addr add 10.1.1.1/24 dev dummy0 ip xfrm policy add src 10.1.1.1/32 dst 10.1.1.2/32 dir out tmpl src fc00::dead:1 dst fc00::dead:2 proto esp reqid 1 mode iptfs level use tmpl src fc00::dead:1 dst fc00::dead:2 proto esp reqid 2 mode transport ping -W 1 -c 1 10.1.1.2 PING 10.1.1.2 (10.1.1.2) 56(84) bytes of data. [ 64.168420] ================================================================== [ 64.169977] BUG: KASAN: stack-out-of-bounds in __xfrm6_addr_hash+0x11e/0x170 [ 64.169977] Read of size 4 at addr ffff88800e1ffd20 by task ping/2844 [ 64.169977] CPU: 2 UID: 0 PID: 2844 Comm: ping Not tainted 7.1.0-rc7-00180-geb23b588430a #98 PREEMPT(full) [ 64.169977] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 64.169977] Call Trace: [ 64.169977] <TASK> [ 64.169977] dump_stack_lvl+0x47/0x70 [ 64.169977] ? __xfrm6_addr_hash+0x11e/0x170 [ 64.169977] print_report+0x152/0x4b0 [ 64.169977] ? ksys_mmap_pgoff+0x6d/0xa0 [ 64.169977] ? entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 64.169977] ? rcu_read_unlock_sched+0xa/0x20 [ 64.169977] ? __virt_addr_valid+0x21b/0x230 [ 64.169977] ? __xfrm6_addr_hash+0x11e/0x170 [ 64.169977] kasan_report+0xa8/0xd0 [ 64.169977] ? __xfrm6_addr_hash+0x11e/0x170 [ 64.169977] __xfrm6_addr_hash+0x11e/0x170 [ 64.169977] __xfrm_dst_hash+0x24/0xc0 [ 64.169977] xfrm_state_find+0xa2d/0x2f90 [ 64.169977] ? __pfx_xfrm_state_find+0x10/0x10 [ 64.169977] ? __pfx_ftrace_graph_ret_addr+0x10/0x10 [ 64.169977] ? __pfx_ftrace_graph_ret_addr+0x10/0x10 [ 64.169977] xfrm_tmpl_resolve_one+0x210/0x570 [ 64.169977] ? __pfx_xfrm_tmpl_resolve_one+0x10/0x10 [ 64.169977] ? __pfx_stack_trace_consume_entry+0x10/0x10 [ 64.169977] ? kernel_text_address+0x5b/0x80 [ 64.169977] ? __kernel_text_address+0xe/0x30 [ 64.169977] ? unwind_get_return_address+0x5e/0x90 [ 64.169977] ? arch_stack_walk+0x8c/0xe0 [ 64.169977] xfrm_tmpl_resolve+0x130/0x200 [ 64.169977] ? __pfx_xfrm_tmpl_resolve+0x10/0x10 [ 64.169977] ? __pfx_xfrm_policy_inexact_lookup_rcu+0x10/0x10 [ 64.169977] ? __refcount_add_not_zero.constprop.0+0xb2/0x110 [ 64.169977] ? __pfx___refcount_add_not_zero.constprop.0+0x10/0x10 [ 64.169977] xfrm_resolve_and_create_bundle+0xd5/0x310 [ 64.169977] ? __pfx_xfrm_resolve_and_create_bundle+0x10/0x10 [ 64.169977] ? __pfx_xfrm_policy_lookup_bytype+0x10/0x10 [ 64.169977] ? __pfx_xfrm_policy_lookup_bytype+0x10/0x10 [ 64.169977] xfrm_lookup_with_ifid+0x3d8/0xb80 [ 64.169977] ? __pfx_xfrm_lookup_with_ifid+0x10/0x10 [ 64.169977] ? ip_route_output_key_hash+0xc6/0x110 [ 64.169977] ? kasan_save_track+0x10/0x30 [ 64.169977] xfrm_lookup_route+0x18/0xe0 [ 64.169977] ip4_datagram_release_cb+0x4c9/0x530 [ 64.169977] ? __pfx_ip4_datagram_release_cb+0x10/0x10 [ 64.169977] ? do_raw_spin_lock+0x71/0xc0 [ 64.169977] ? __pfx_do_raw_spin_lock+0x10/0x10 [ 64.169977] release_sock+0xb0/0x170 [ 64.169977] udp_connect+0x43/0x50 [ 64.169977] __sys_connect+0xa6/0x100 [ 64.169977] ? alloc_fd+0x2e9/0x300 [ 64.169977] ? __pfx___sys_connect+0x10/0x10 [ 64.169977] ? preempt_latency ---truncated---
Title xfrm: reject optional IPTFS templates in outbound policies
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-08-10T12:04:40.933Z

Reserved: 2026-07-30T09:28:09.392Z

Link: CVE-2026-68420

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-10T16:00:04Z

Weaknesses