{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2023-53500",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2025-10-01T11:39:39.404Z",
        "datePublished": "2025-10-01T11:45:51.182Z",
        "dateUpdated": "2026-08-05T09:14:29.679Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
                "shortName": "Linux",
                "dateUpdated": "2026-08-05T09:14:29.679Z"
            },
            "descriptions": [
                {
                    "lang": "en",
                    "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: fix slab-use-after-free in decode_session6\n\nWhen the xfrm device is set to the qdisc of the sfb type, the cb field\nof the sent skb may be modified during enqueuing. Then,\nslab-use-after-free may occur when the xfrm device sends IPv6 packets.\n\nThe stack information is as follows:\nBUG: KASAN: slab-use-after-free in decode_session6+0x103f/0x1890\nRead of size 1 at addr ffff8881111458ef by task swapper/3/0\nCPU: 3 PID: 0 Comm: swapper/3 Not tainted 6.4.0-next-20230707 #409\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014\nCall Trace:\n<IRQ>\ndump_stack_lvl+0xd9/0x150\nprint_address_description.constprop.0+0x2c/0x3c0\nkasan_report+0x11d/0x130\ndecode_session6+0x103f/0x1890\n__xfrm_decode_session+0x54/0xb0\nxfrmi_xmit+0x173/0x1ca0\ndev_hard_start_xmit+0x187/0x700\nsch_direct_xmit+0x1a3/0xc30\n__qdisc_run+0x510/0x17a0\n__dev_queue_xmit+0x2215/0x3b10\nneigh_connected_output+0x3c2/0x550\nip6_finish_output2+0x55a/0x1550\nip6_finish_output+0x6b9/0x1270\nip6_output+0x1f1/0x540\nndisc_send_skb+0xa63/0x1890\nndisc_send_rs+0x132/0x6f0\naddrconf_rs_timer+0x3f1/0x870\ncall_timer_fn+0x1a0/0x580\nexpire_timers+0x29b/0x4b0\nrun_timer_softirq+0x326/0x910\n__do_softirq+0x1d4/0x905\nirq_exit_rcu+0xb7/0x120\nsysvec_apic_timer_interrupt+0x97/0xc0\n</IRQ>\n<TASK>\nasm_sysvec_apic_timer_interrupt+0x1a/0x20\nRIP: 0010:intel_idle_hlt+0x23/0x30\nCode: 1f 84 00 00 00 00 00 f3 0f 1e fa 41 54 41 89 d4 0f 1f 44 00 00 66 90 0f 1f 44 00 00 0f 00 2d c4 9f ab 00 0f 1f 44 00 00 fb f4 <fa> 44 89 e0 41 5c c3 66 0f 1f 44 00 00 f3 0f 1e fa 41 54 41 89 d4\nRSP: 0018:ffffc90000197d78 EFLAGS: 00000246\nRAX: 00000000000a83c3 RBX: ffffe8ffffd09c50 RCX: ffffffff8a22d8e5\nRDX: 0000000000000001 RSI: ffffffff8d3f8080 RDI: ffffe8ffffd09c50\nRBP: ffffffff8d3f8080 R08: 0000000000000001 R09: ffffed1026ba6d9d\nR10: ffff888135d36ceb R11: 0000000000000001 R12: 0000000000000001\nR13: ffffffff8d3f8100 R14: 0000000000000001 R15: 0000000000000000\ncpuidle_enter_state+0xd3/0x6f0\ncpuidle_enter+0x4e/0xa0\ndo_idle+0x2fe/0x3c0\ncpu_startup_entry+0x18/0x20\nstart_secondary+0x200/0x290\nsecondary_startup_64_no_verify+0x167/0x16b\n</TASK>\nAllocated by task 939:\nkasan_save_stack+0x22/0x40\nkasan_set_track+0x25/0x30\n__kasan_slab_alloc+0x7f/0x90\nkmem_cache_alloc_node+0x1cd/0x410\nkmalloc_reserve+0x165/0x270\n__alloc_skb+0x129/0x330\ninet6_ifa_notify+0x118/0x230\n__ipv6_ifa_notify+0x177/0xbe0\naddrconf_dad_completed+0x133/0xe00\naddrconf_dad_work+0x764/0x1390\nprocess_one_work+0xa32/0x16f0\nworker_thread+0x67d/0x10c0\nkthread+0x344/0x440\nret_from_fork+0x1f/0x30\nThe buggy address belongs to the object at ffff888111145800\nwhich belongs to the cache skbuff_small_head of size 640\nThe buggy address is located 239 bytes inside of\nfreed 640-byte region [ffff888111145800, ffff888111145a80)\n\nAs commit f855691975bb (\"xfrm6: Fix the nexthdr offset in\n_decode_session6.\") showed, xfrm_decode_session was originally intended\nonly for the receive path. IP6CB(skb)->nhoff is not set during\ntransmission. Therefore, set the cb field in the skb to 0 before\nsending packets."
                }
            ],
            "metrics": [
                {
                    "cvssV3_1": {
                        "version": "3.1",
                        "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H",
                        "baseScore": 7.3,
                        "baseSeverity": "HIGH"
                    },
                    "scenarios": [
                        {
                            "lang": "en",
                            "value": "AV:L - Triggering requires locally configuring an xfrm interface and attaching a cb-dirtying qdisc (sfb) via rtnetlink/tc, then emitting IPv6 packets out that device — all local netlink operations. A remote peer can only trigger it opportunistically on a pre-existing xfrm+fq/sfb deployment, so the vector the attacker can actually establish is local.\nAC:L - The attacker fully controls every precondition: create the xfrm link, attach `sfb` with `rehash 1` to force the slot that leaves a non-zero hash in skb->cb[14..15], and transmit IPv6 packets at will with unlimited free retries. There is no race to win and no memory layout or victim state outside the attacker's influence.\nPR:L - Both RTM_NEWLINK and RTM_NEWQDISC gate only on `netlink_net_capable(skb, CAP_NET_ADMIN)`, which resolves to `ns_capable(net->user_ns, CAP_NET_ADMIN)` and is therefore satisfied by an unprivileged user inside `unshare -Urn`; the required sch_sfb and xfrm_interface modules autoload. No real root in the init namespace is needed.\nUI:N - Once the device is brought up, IPv6 addrconf on the ARPHRD_NONE xfrm interface sends router solicitations by itself (exactly the addrconf_rs_timer path in the KASAN trace), and the attacker can additionally send traffic on demand. No victim action is involved.\nS:U - The out-of-bounds read, the resulting bad policy decision, and any oops all occur within the host kernel's own security authority. No hypervisor, IOMMU, or sandbox boundary is crossed.\nC:H - `nh[nhoff]` reads a byte at an entirely uncontrolled offset of up to 65535 past a ~640-byte slab object, confirmed by KASAN to land inside freed heap memory, and each packet re-randomizes the offset so an attacker can sweep a 64 KB window of adjacent kernel memory. The recovered byte becomes `flowi6_proto` and steers the xfrm policy/route lookup, providing an observable oracle for that out-of-bounds content.\nI:L - There is no write or corruption primitive — the stale byte only lands in an on-stack `flowi6` — but it causes `xfrm_lookup_with_ifid()` to select the wrong policy/SA, so outbound tunnel packets can be emitted under an unintended security association (the \"incorrect policy lookups\" failure f855691975bb was written to prevent). That is a real but limited modification of the security decision.\nA:H - A read up to 64 KB beyond the slab object can hit an unmapped or guarded page, faulting in softirq context for an immediate oops/panic, and on KASAN or hardened kernels it reports and panics outright. Independently, the garbage flow decode makes `xfrm_lookup` fail so `xfrmi_xmit2()` drops every IPv6 packet on the interface, taking the IPsec tunnel down."
                        }
                    ]
                }
            ],
            "affected": [
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "net/xfrm/xfrm_interface_core.c"
                    ],
                    "versions": [
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                            "version": "f855691975bb06373a98711e4cfe2c224244b536",
                            "lessThan": "da4cbaa75ed088b6d70db77b9103a27e2359e243",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "f855691975bb06373a98711e4cfe2c224244b536",
                            "lessThan": "db0e50741f0387f388e9ec824ea7ae8456554d5b",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "f855691975bb06373a98711e4cfe2c224244b536",
                            "lessThan": "bafa236380816b41b2c4c6970d9067fefa4a6c9e",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "f855691975bb06373a98711e4cfe2c224244b536",
                            "lessThan": "44b3d40967009304617a7a6486490c1d6c12f899",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "f855691975bb06373a98711e4cfe2c224244b536",
                            "lessThan": "0d27567fde5be5f0edc2db5c110142b7915b8fa8",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "f855691975bb06373a98711e4cfe2c224244b536",
                            "lessThan": "86f15300a22656db3fa8c8967defbcd24fac4d37",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "f855691975bb06373a98711e4cfe2c224244b536",
                            "lessThan": "53223f2ed1ef5c90dad814daaaefea4e68a933c8",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                },
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "net/xfrm/xfrm_interface_core.c"
                    ],
                    "versions": [
                        {
                            "version": "3.19",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "3.19",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "4.19.293",
                            "lessThanOrEqual": "4.19.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "5.4.255",
                            "lessThanOrEqual": "5.4.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "5.10.192",
                            "lessThanOrEqual": "5.10.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "5.15.128",
                            "lessThanOrEqual": "5.15.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.1.47",
                            "lessThanOrEqual": "6.1.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.4.12",
                            "lessThanOrEqual": "6.4.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.5",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }
            ],
            "cpeApplicability": [
                {
                    "nodes": [
                        {
                            "operator": "OR",
                            "negate": false,
                            "cpeMatch": [
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "3.19",
                                    "versionEndExcluding": "4.19.293"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "3.19",
                                    "versionEndExcluding": "5.4.255"
                                },
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                                    "versionStartIncluding": "3.19",
                                    "versionEndExcluding": "6.1.47"
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                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "3.19",
                                    "versionEndExcluding": "6.4.12"
                                },
                                {
                                    "vulnerable": true,
                                    "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                                    "versionStartIncluding": "3.19",
                                    "versionEndExcluding": "6.5"
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                }
            ],
            "references": [
                {
                    "url": "https://git.kernel.org/stable/c/da4cbaa75ed088b6d70db77b9103a27e2359e243"
                },
                {
                    "url": "https://git.kernel.org/stable/c/db0e50741f0387f388e9ec824ea7ae8456554d5b"
                },
                {
                    "url": "https://git.kernel.org/stable/c/bafa236380816b41b2c4c6970d9067fefa4a6c9e"
                },
                {
                    "url": "https://git.kernel.org/stable/c/44b3d40967009304617a7a6486490c1d6c12f899"
                },
                {
                    "url": "https://git.kernel.org/stable/c/0d27567fde5be5f0edc2db5c110142b7915b8fa8"
                },
                {
                    "url": "https://git.kernel.org/stable/c/86f15300a22656db3fa8c8967defbcd24fac4d37"
                },
                {
                    "url": "https://git.kernel.org/stable/c/53223f2ed1ef5c90dad814daaaefea4e68a933c8"
                }
            ],
            "title": "xfrm: fix slab-use-after-free in decode_session6",
            "x_generator": {
                "engine": "bippy-1.2.0"
            }
        }
    }
}