{"cve":"CVE-2026-68420","nvd":{"published":"2026-08-10T13:20:35.840","modified":"2026-08-17T06:17:51.013","status":"Received","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: reject optional IPTFS templates in outbound policies\n\nsyzbot reported a stack-out-of-bounds read in xfrm_state_find()\nwhich flows from xfrm_tmpl_resolve_one().\n\nCommit 3d776e31c841 (\"xfrm: Reject optional tunnel/BEET mode\ntemplates in outbound policies\") disallowed optional tunnel and\nBEET in outbound policies to prevent this. Later when IPTFS\nadded, it was not covered by that fix and can still trigger\nthe out-of-bounds read;\n\nExtend the check to disallow optional IPTFS in outbound policies\nas well. IPTFS should be identical to tunnel mode.\nIN and FWD policies are not affected: xfrm_tmpl_resolve_one()\nis only reachable via the outbound path.\n\nReproducer, before:\n\nip link add dummy0 type dummy\nip link set dummy0 up\nip addr add 10.1.1.1/24 dev dummy0\nip xfrm policy add src 10.1.1.1/32 dst 10.1.1.2/32 dir out tmpl\n  src fc00::dead:1 dst fc00::dead:2 proto esp reqid 1 mode iptfs\n  level use tmpl src fc00::dead:1 dst fc00::dead:2 proto esp reqid\n  2 mode transport\nping -W 1 -c 1 10.1.1.2\nPING 10.1.1.2 (10.1.1.2) 56(84) bytes of data.\n\n[   64.168420] ==================================================================\n[   64.169977] BUG: KASAN: stack-out-of-bounds in __xfrm6_addr_hash+0x11e/0x170\n[   64.169977] Read of size 4 at addr ffff88800e1ffd20 by task ping/2844\n\n[   64.169977] CPU: 2 UID: 0 PID: 2844 Comm: ping Not tainted 7.1.0-rc7-00180-geb23b588430a #98 PREEMPT(full)\n[   64.169977] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\n[   64.169977] Call Trace:\n[   64.169977]  <TASK>\n[   64.169977]  dump_stack_lvl+0x47/0x70\n[   64.169977]  ? __xfrm6_addr_hash+0x11e/0x170\n[   64.169977]  print_report+0x152/0x4b0\n[   64.169977]  ? ksys_mmap_pgoff+0x6d/0xa0\n[   64.169977]  ? entry_SYSCALL_64_after_hwframe+0x76/0x7e\n[   64.169977]  ? rcu_read_unlock_sched+0xa/0x20\n[   64.169977]  ? __virt_addr_valid+0x21b/0x230\n[   64.169977]  ? __xfrm6_addr_hash+0x11e/0x170\n[   64.169977]  kasan_report+0xa8/0xd0\n[   64.169977]  ? __xfrm6_addr_hash+0x11e/0x170\n[   64.169977]  __xfrm6_addr_hash+0x11e/0x170\n[   64.169977]  __xfrm_dst_hash+0x24/0xc0\n[   64.169977]  xfrm_state_find+0xa2d/0x2f90\n[   64.169977]  ? __pfx_xfrm_state_find+0x10/0x10\n[   64.169977]  ? __pfx_ftrace_graph_ret_addr+0x10/0x10\n[   64.169977]  ? __pfx_ftrace_graph_ret_addr+0x10/0x10\n[   64.169977]  xfrm_tmpl_resolve_one+0x210/0x570\n[   64.169977]  ? __pfx_xfrm_tmpl_resolve_one+0x10/0x10\n[   64.169977]  ? __pfx_stack_trace_consume_entry+0x10/0x10\n[   64.169977]  ? kernel_text_address+0x5b/0x80\n[   64.169977]  ? __kernel_text_address+0xe/0x30\n[   64.169977]  ? unwind_get_return_address+0x5e/0x90\n[   64.169977]  ? arch_stack_walk+0x8c/0xe0\n[   64.169977]  xfrm_tmpl_resolve+0x130/0x200\n[   64.169977]  ? __pfx_xfrm_tmpl_resolve+0x10/0x10\n[   64.169977]  ? __pfx_xfrm_policy_inexact_lookup_rcu+0x10/0x10\n[   64.169977]  ? __refcount_add_not_zero.constprop.0+0xb2/0x110\n[   64.169977]  ? __pfx___refcount_add_not_zero.constprop.0+0x10/0x10\n[   64.169977]  xfrm_resolve_and_create_bundle+0xd5/0x310\n[   64.169977]  ? __pfx_xfrm_resolve_and_create_bundle+0x10/0x10\n[   64.169977]  ? __pfx_xfrm_policy_lookup_bytype+0x10/0x10\n[   64.169977]  ? __pfx_xfrm_policy_lookup_bytype+0x10/0x10\n[   64.169977]  xfrm_lookup_with_ifid+0x3d8/0xb80\n[   64.169977]  ? __pfx_xfrm_lookup_with_ifid+0x10/0x10\n[   64.169977]  ? ip_route_output_key_hash+0xc6/0x110\n[   64.169977]  ? kasan_save_track+0x10/0x30\n[   64.169977]  xfrm_lookup_route+0x18/0xe0\n[   64.169977]  ip4_datagram_release_cb+0x4c9/0x530\n[   64.169977]  ? __pfx_ip4_datagram_release_cb+0x10/0x10\n[   64.169977]  ? do_raw_spin_lock+0x71/0xc0\n[   64.169977]  ? __pfx_do_raw_spin_lock+0x10/0x10\n[   64.169977]  release_sock+0xb0/0x170\n[   64.169977]  udp_connect+0x43/0x50\n[   64.169977]  __sys_connect+0xa6/0x100\n[   64.169977]  ? alloc_fd+0x2e9/0x300\n[   64.169977]  ? __pfx___sys_connect+0x10/0x10\n[   64.169977]  ? preempt_latency\n---truncated---","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","score":7.1},"cwes":[],"references":["https://git.kernel.org/stable/c/9333f4b6f44858fc98eb12bf26b8d2959eb975d5","https://git.kernel.org/stable/c/d7fc6f351c478586980a521d63b0214d9c055e78","https://git.kernel.org/stable/c/ea528f18231ec0f33317be57f8866913b19aba6e"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:47:54.990491175+00:00"},"epss":{"cve":"CVE-2026-68420","score":0.00115,"percentile":0.01552,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}