# CVE-2026-68420: linux: In the Linux kernel, the following vulnerability has been resolved: xfrm: reject optional IPTFS templates in outboun... CVE-2026-68420 is fixed in 20 products on 1 platform, first by DEBIAN-CVE-2026-68420, released August 11, 2026. It is not reported as exploited. Patch Radar priority: High. - Web page: https://patchblox.com/security/cve/CVE-2026-68420 - Priority: High - CVSS: 7.1 (high) - EPSS: 0.0012 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Aug 10, 2026 ## 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] [ 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--- ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | bpftool6.18 amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | bpftool6.18-debuginfo amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel-livepatch-6.18.44-99.149 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18 amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-debuginfo amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-debuginfo-common-aarch64 amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-debuginfo-common-x86_64 amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-devel amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-headers amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-modules-extra amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-modules-extra-common amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-tools amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-tools-debuginfo amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | kernel6.18-tools-devel amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | linux Debian 14 | 7.1.6-1 | [DEBIAN-CVE-2026-68420](https://patchblox.com/security/data/fix/linux/debian-cve-2026-68420.md) | Aug 11, 2026 | | Linux | microvm-kernel6.18 amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | perf6.18 amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | perf6.18-debuginfo amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | python3-perf6.18 amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | | Linux | python3-perf6.18-debuginfo amzn 2023 | 1:6.18.44-99.149.amzn2023 | [ALAS2023-2026-2106](https://patchblox.com/security/data/fix/linux/alas2023-2026-2106.md) | Aug 31, 2026 | --- Data as of 2026-11-08T06:59:42Z UTC. 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