{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-68420", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-68420" ], "published": "2026-08-10T12:08:00Z", "summary": "xfrm: reject optional IPTFS templates in outbound policies", "details": "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] \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---", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:13", "name": "linux" }, "versions": [ "1:6.18.29-1+rpt1", "1:6.18.33-1+rpt1", "1:6.18.34-1+rpt1", "1:6.18.39-1+rpt1" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.18.29+rpt-rpi-2712", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v6", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v7", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v8", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v8-rt", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-2712", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v6", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v7", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v8", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v8-rt", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-2712", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v6", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v7", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v8", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v8-rt", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-2712", "binary_version": "1:6.18.39-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-v6", "binary_version": "1:6.18.39-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-v7", "binary_version": "1:6.18.39-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-v8", "binary_version": "1:6.18.39-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-v8-rt", "binary_version": "1:6.18.39-1+rpt1" } ] }, "database_specific": { "per_version": { "1:6.18.29-1+rpt1": { "linux_commit": "66318c5b5cd8145a662303af12ed39ac07eb27cc", "upstream_version": "6.18.29", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.42" }, "1:6.18.33-1+rpt1": { "linux_commit": "95b85bebbedcaedfa7ca79116ed38b7376fba412", "upstream_version": "6.18.33", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.42" }, "1:6.18.34-1+rpt1": { "linux_commit": "c8c7494100e99ee05b11aaa4f0588a223a63d1af", "upstream_version": "6.18.34", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.42" }, "1:6.18.39-1+rpt1": { "linux_commit": "60ea684a8ace97bb0db1a16e20753bdd6ab371ff", "upstream_version": "6.18.39", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.42" } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-68420" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/d7fc6f351c478586980a521d63b0214d9c055e78" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/9333f4b6f44858fc98eb12bf26b8d2959eb975d5" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/ea528f18231ec0f33317be57f8866913b19aba6e" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-17T05:24:08Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.1, "cvss_v3_severity": "High", "scenario": "AV:L - The attacker must install an XFRM policy over the AF_KEY/XFRM netlink socket and then originate local traffic (connect()/sendto()) matching that policy, so the entire path requires local access to the machine; no remote packet reaches this code.\nAC:L - The reproducer is deterministic \u2014 add one outbound policy with an optional IPTFS template plus a following transport-mode template of a different family, then send one packet; no race, no memory-layout dependence, and CONFIG_XFRM is enabled on all mainstream distros.\nPR:L - xfrm_user_rcv_msg() checks netlink_net_capable(CAP_NET_ADMIN), which resolves to ns_capable(net->user_ns, CAP_NET_ADMIN); an unprivileged user obtains this with \"unshare -Urn\" and can create the dummy device, the policy, and the triggering traffic entirely inside that namespace.\nUI:N - The attacker performs every step \u2014 policy insertion and packet transmission \u2014 with no action by any other user or administrator.\nS:U - The out-of-bounds read stays within the kernel's own stack and the affected resources are managed by the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - __xfrm6_addr_hash() reads 16 bytes from a 4-byte on-stack IPv4 address, exposing adjacent kernel stack contents; with zeroed template addresses xfrm_init_tempstate() copies those bytes into the acquire state, which is broadcast to userspace via XFRM_MSG_ACQUIRE, leaking kernel stack data (potentially pointers usable for KASLR defeat).\nI:N - The defect is purely a read of out-of-bounds stack memory; no kernel memory is written out of bounds and no control-flow or data structure is corrupted by the attacker.\nA:H - The invalid access is a KASAN-detected stack out-of-bounds read that taints the kernel and terminates the machine on kernels built with KASAN or panic_on_warn, and the bogus state derived from garbage addresses can be re-triggered at will by an unprivileged user." } } }