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CVE-2023-53500 (GCVE-0-2023-53500)

Vulnerability from cvelistv5 – Published: 2025-10-01 11:45 – Updated: 2026-08-05 09:14
VLAI
Title
xfrm: fix slab-use-after-free in decode_session6
Summary
In the Linux kernel, the following vulnerability has been resolved: xfrm: fix slab-use-after-free in decode_session6 When the xfrm device is set to the qdisc of the sfb type, the cb field of the sent skb may be modified during enqueuing. Then, slab-use-after-free may occur when the xfrm device sends IPv6 packets. The stack information is as follows: BUG: KASAN: slab-use-after-free in decode_session6+0x103f/0x1890 Read of size 1 at addr ffff8881111458ef by task swapper/3/0 CPU: 3 PID: 0 Comm: swapper/3 Not tainted 6.4.0-next-20230707 #409 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014 Call Trace: <IRQ> dump_stack_lvl+0xd9/0x150 print_address_description.constprop.0+0x2c/0x3c0 kasan_report+0x11d/0x130 decode_session6+0x103f/0x1890 __xfrm_decode_session+0x54/0xb0 xfrmi_xmit+0x173/0x1ca0 dev_hard_start_xmit+0x187/0x700 sch_direct_xmit+0x1a3/0xc30 __qdisc_run+0x510/0x17a0 __dev_queue_xmit+0x2215/0x3b10 neigh_connected_output+0x3c2/0x550 ip6_finish_output2+0x55a/0x1550 ip6_finish_output+0x6b9/0x1270 ip6_output+0x1f1/0x540 ndisc_send_skb+0xa63/0x1890 ndisc_send_rs+0x132/0x6f0 addrconf_rs_timer+0x3f1/0x870 call_timer_fn+0x1a0/0x580 expire_timers+0x29b/0x4b0 run_timer_softirq+0x326/0x910 __do_softirq+0x1d4/0x905 irq_exit_rcu+0xb7/0x120 sysvec_apic_timer_interrupt+0x97/0xc0 </IRQ> <TASK> asm_sysvec_apic_timer_interrupt+0x1a/0x20 RIP: 0010:intel_idle_hlt+0x23/0x30 Code: 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 RSP: 0018:ffffc90000197d78 EFLAGS: 00000246 RAX: 00000000000a83c3 RBX: ffffe8ffffd09c50 RCX: ffffffff8a22d8e5 RDX: 0000000000000001 RSI: ffffffff8d3f8080 RDI: ffffe8ffffd09c50 RBP: ffffffff8d3f8080 R08: 0000000000000001 R09: ffffed1026ba6d9d R10: ffff888135d36ceb R11: 0000000000000001 R12: 0000000000000001 R13: ffffffff8d3f8100 R14: 0000000000000001 R15: 0000000000000000 cpuidle_enter_state+0xd3/0x6f0 cpuidle_enter+0x4e/0xa0 do_idle+0x2fe/0x3c0 cpu_startup_entry+0x18/0x20 start_secondary+0x200/0x290 secondary_startup_64_no_verify+0x167/0x16b </TASK> Allocated by task 939: kasan_save_stack+0x22/0x40 kasan_set_track+0x25/0x30 __kasan_slab_alloc+0x7f/0x90 kmem_cache_alloc_node+0x1cd/0x410 kmalloc_reserve+0x165/0x270 __alloc_skb+0x129/0x330 inet6_ifa_notify+0x118/0x230 __ipv6_ifa_notify+0x177/0xbe0 addrconf_dad_completed+0x133/0xe00 addrconf_dad_work+0x764/0x1390 process_one_work+0xa32/0x16f0 worker_thread+0x67d/0x10c0 kthread+0x344/0x440 ret_from_fork+0x1f/0x30 The buggy address belongs to the object at ffff888111145800 which belongs to the cache skbuff_small_head of size 640 The buggy address is located 239 bytes inside of freed 640-byte region [ffff888111145800, ffff888111145a80) As commit f855691975bb ("xfrm6: Fix the nexthdr offset in _decode_session6.") showed, xfrm_decode_session was originally intended only for the receive path. IP6CB(skb)->nhoff is not set during transmission. Therefore, set the cb field in the skb to 0 before sending packets.
Severity
7.3 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: f855691975bb06373a98711e4cfe2c224244b536 , < da4cbaa75ed088b6d70db77b9103a27e2359e243 (git)
Affected: f855691975bb06373a98711e4cfe2c224244b536 , < db0e50741f0387f388e9ec824ea7ae8456554d5b (git)
Affected: f855691975bb06373a98711e4cfe2c224244b536 , < bafa236380816b41b2c4c6970d9067fefa4a6c9e (git)
Affected: f855691975bb06373a98711e4cfe2c224244b536 , < 44b3d40967009304617a7a6486490c1d6c12f899 (git)
Affected: f855691975bb06373a98711e4cfe2c224244b536 , < 0d27567fde5be5f0edc2db5c110142b7915b8fa8 (git)
Affected: f855691975bb06373a98711e4cfe2c224244b536 , < 86f15300a22656db3fa8c8967defbcd24fac4d37 (git)
Affected: f855691975bb06373a98711e4cfe2c224244b536 , < 53223f2ed1ef5c90dad814daaaefea4e68a933c8 (git)
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Linux Linux Affected: 3.19
Unaffected: 0 , < 3.19 (semver)
Unaffected: 4.19.293 , ≤ 4.19.* (semver)
Unaffected: 5.4.255 , ≤ 5.4.* (semver)
Unaffected: 5.10.192 , ≤ 5.10.* (semver)
Unaffected: 5.15.128 , ≤ 5.15.* (semver)
Unaffected: 6.1.47 , ≤ 6.1.* (semver)
Unaffected: 6.4.12 , ≤ 6.4.* (semver)
Unaffected: 6.5 , ≤ * (original_commit_for_fix)
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{
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      "cpeApplicability": [
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              "operator": "OR"
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      "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\u003cIRQ\u003e\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\u003c/IRQ\u003e\n\u003cTASK\u003e\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 \u003cfa\u003e 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\u003c/TASK\u003e\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)-\u003enhoff is not set during\ntransmission. Therefore, set the cb field in the skb to 0 before\nsending packets."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.3,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H",
            "version": "3.1"
          },
          "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 \u2014 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-\u003ecb[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\u0027s 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-\u003euser_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\u0027s 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 \u2014 the stale byte only lands in an on-stack `flowi6` \u2014 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."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T09:14:29.679Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "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"
      }
    }
  },
  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2023-53500",
    "datePublished": "2025-10-01T11:45:51.182Z",
    "dateReserved": "2025-10-01T11:39:39.404Z",
    "dateUpdated": "2026-08-05T09:14:29.679Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
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      "date": "2026-09-19",
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        "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\u003cIRQ\u003e\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\u003c/IRQ\u003e\n\u003cTASK\u003e\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 \u003cfa\u003e 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\u003c/TASK\u003e\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)-\u003enhoff is not set during\ntransmission. Therefore, set the cb field in the skb to 0 before\nsending packets."
          }
        ],
        "id": "CVE-2023-53500",
        "lastModified": "2026-08-04T10:19:09.653",
        "metrics": {
          "cvssMetricV31": [
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              "cvssData": {
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                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.3,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "LOW",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H",
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              "exploitabilityScore": 1.8,
              "impactScore": 5.9,
              "source": "nvd@nist.gov",
              "type": "Primary"
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        "published": "2025-10-01T12:15:53.490",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Modified",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-416"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
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    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-04T19:17:58+00:00",
      "cve": "CVE-2023-53500",
      "id": "CVE-2023-53500",
      "initial_release_date": "2023-01-01T00:00:00+00:00",
      "product_status:known_affected": "156",
      "product_status:known_not_affected": "118",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: xfrm: fix slab-use-after-free in decode_session6",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2023/cve-2023-53500.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-11T02:20:52Z",
      "cve": "CVE-2023-53500",
      "id": "CVE-2023-53500",
      "initial_release_date": "2025-10-01T23:30:06Z",
      "product_status:known_affected": "502",
      "product_status:known_not_affected": "15",
      "product_status:recommended": "581",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2023-53500",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2023-53500.json",
      "version": "60"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.