CVE-2026-74715 (GCVE-0-2026-74715)

Vulnerability from cvelistv5 – Published: 2026-08-22 15:33 – Updated: 2026-10-16 19:16
VLAI
Title
bpf: Fix netns reference imbalance in conntrack kfuncs
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix netns reference imbalance in conntrack kfuncs The opts argument of the BPF conntrack kfuncs can point to a shared map value. __bpf_nf_ct_lookup() and __bpf_nf_ct_alloc_entry() read opts->netns_id separately when acquiring and releasing the network namespace reference. The reference imbalance can occur as follows: CPU 0 CPU 1 read opts->netns_id (-1) skip get_net_ns_by_id() write opts->netns_id (id) read opts->netns_id (id) put_net(net) /* no matching get */ The reverse transition leaks the reference. Repeating the unmatched put can destroy a live namespace and crash later users. The kernel reported: Oops: general protection fault, probably for non-canonical address KASAN: null-ptr-deref in range [0x00000000000000e8-0x00000000000000ef] RIP: 0010:bpf_prog_test_run_xdp+0x52c/0x1700 Call Trace: __sys_bpf+0x1662/0x50c0 __x64_sys_bpf+0x73/0xb0 do_syscall_64+0xf9/0x540 entry_SYSCALL_64_after_hwframe+0x77/0x7f Kernel panic - not syncing: Fatal exception Snapshot every input field of opts with READ_ONCE() before validating or using it. The netns_id snapshot keeps the namespace get/put pair balanced, while the other snapshots keep the remaining options from changing partway through an invocation. The individual reads can still observe an inconsistent combination during a concurrent update, but each selected field value remains stable for that invocation.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 19:15 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6666 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: aed8ee7feb44b6537af1e0b4f03365d42928be38 , < 4af94462c0ca2187a02a1a6641020ae888c74d5c (git)
Affected: aed8ee7feb44b6537af1e0b4f03365d42928be38 , < e5e060eb63d10b41ab60fd955649479d99b38210 (git)
Affected: aed8ee7feb44b6537af1e0b4f03365d42928be38 , < fdeba03fea78407a8c52faa99177c9f7f29f90eb (git)
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Linux Linux Affected: 6.0
Unaffected: 0 , < 6.0 (semver)
Unaffected: 6.18.57 , ≤ 6.18.* (semver)
Unaffected: 7.1.9 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix netns reference imbalance in conntrack kfuncs\n\nThe opts argument of the BPF conntrack kfuncs can point to a shared\nmap value.  __bpf_nf_ct_lookup() and __bpf_nf_ct_alloc_entry() read\nopts-\u003enetns_id separately when acquiring and releasing the network\nnamespace reference.\n\nThe reference imbalance can occur as follows:\n\n  CPU 0                                  CPU 1\n  read opts-\u003enetns_id (-1)\n  skip get_net_ns_by_id()\n                                         write opts-\u003enetns_id (id)\n  read opts-\u003enetns_id (id)\n  put_net(net) /* no matching get */\n\nThe reverse transition leaks the reference.  Repeating the unmatched put\ncan destroy a live namespace and crash later users.\n\nThe kernel reported:\n\n  Oops: general protection fault, probably for non-canonical address\n  KASAN: null-ptr-deref in range [0x00000000000000e8-0x00000000000000ef]\n  RIP: 0010:bpf_prog_test_run_xdp+0x52c/0x1700\n  Call Trace:\n   __sys_bpf+0x1662/0x50c0\n   __x64_sys_bpf+0x73/0xb0\n   do_syscall_64+0xf9/0x540\n   entry_SYSCALL_64_after_hwframe+0x77/0x7f\n  Kernel panic - not syncing: Fatal exception\n\nSnapshot every input field of opts with READ_ONCE() before validating or\nusing it.  The netns_id snapshot keeps the namespace get/put pair\nbalanced, while the other snapshots keep the remaining options from\nchanging partway through an invocation.  The individual reads can still\nobserve an inconsistent combination during a concurrent update, but each\nselected field value remains stable for that invocation."
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            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nbpf: Soluciona el desequilibrio de referencia de netns en las kfuncs de conntrack\n\nEl argumento opts de las kfuncs de conntrack de BPF puede apuntar a un valor de mapa compartido. __bpf_nf_ct_lookup() y __bpf_nf_ct_alloc_entry() leen opts -\u003e netns_id por separado al adquirir y liberar la referencia del espacio de nombres de red.\n\nEl desequilibrio de referencia puede ocurrir de la siguiente manera:\n\n  CPU 0                                  CPU 1\n  lee opts -\u003e netns_id (-1)\n  omite get_net_ns_by_id()\n                                         escribe opts -\u003e netns_id (id)\n  lee opts -\u003e netns_id (id)\n  put_net(net) /* no hay \u0027get\u0027 coincidente */\n\nLa transici\u00f3n inversa filtra la referencia. Repetir el \u0027put\u0027 sin coincidencia puede destruir un espacio de nombres activo y provocar un fallo en usuarios posteriores.\n\nEl kernel inform\u00f3:\n\n  Oops: fallo de protecci\u00f3n general, probablemente por direcci\u00f3n no can\u00f3nica\n  KASAN: null-ptr-deref en el rango [0x00000000000000e8-0x00000000000000ef]\n  RIP: 0010:bpf_prog_test_run_xdp+0x52c/0x1700\n  Call Trace:\n   __sys_bpf+0x1662/0x50c0\n   __x64_sys_bpf+0x73/0xb0\n   do_syscall_64+0xf9/0x540\n   entry_SYSCALL_64_after_hwframe+0x77/0x7f\n  P\u00e1nico del kernel - no sincronizando: Excepci\u00f3n fatal\n\nRealice una instant\u00e1nea de cada campo de entrada de opts con READ_ONCE() antes de validarlo o usarlo. La instant\u00e1nea de netns_id mantiene equilibrado el par \u0027get/put\u0027 del espacio de nombres, mientras que las otras instant\u00e1neas evitan que las opciones restantes cambien a mitad de una invocaci\u00f3n. Las lecturas individuales a\u00fan pueden observar una combinaci\u00f3n inconsistente durante una actualizaci\u00f3n concurrente, pero cada valor de campo seleccionado permanece estable para esa invocaci\u00f3n."
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                  "lessThan": "fdeba03fea78407a8c52faa99177c9f7f29f90eb",
                  "status": "affected",
                  "version": "aed8ee7feb44b6537af1e0b4f03365d42928be38",
                  "versionType": "git"
                }
              ]
            },
            {
              "defaultStatus": "affected",
              "product": "Linux",
              "programFiles": [
                "net/netfilter/nf_conntrack_bpf.c"
              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
                  "status": "affected",
                  "version": "6.0"
                },
                {
                  "lessThan": "6.0",
                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.18.*",
                  "status": "unaffected",
                  "version": "6.18.57",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "7.1.*",
                  "status": "unaffected",
                  "version": "7.1.9",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "7.2",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
            {
              "nodes": [
                {
                  "cpeMatch": [
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.18.57",
                      "versionStartIncluding": "6.0",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "7.1.9",
                      "versionStartIncluding": "6.0",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "7.2",
                      "versionStartIncluding": "6.0",
                      "vulnerable": true
                    }
                  ],
                  "negate": false,
                  "operator": "OR"
                }
              ]
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix netns reference imbalance in conntrack kfuncs\n\nThe opts argument of the BPF conntrack kfuncs can point to a shared\nmap value.  __bpf_nf_ct_lookup() and __bpf_nf_ct_alloc_entry() read\nopts-\u003enetns_id separately when acquiring and releasing the network\nnamespace reference.\n\nThe reference imbalance can occur as follows:\n\n  CPU 0                                  CPU 1\n  read opts-\u003enetns_id (-1)\n  skip get_net_ns_by_id()\n                                         write opts-\u003enetns_id (id)\n  read opts-\u003enetns_id (id)\n  put_net(net) /* no matching get */\n\nThe reverse transition leaks the reference.  Repeating the unmatched put\ncan destroy a live namespace and crash later users.\n\nThe kernel reported:\n\n  Oops: general protection fault, probably for non-canonical address\n  KASAN: null-ptr-deref in range [0x00000000000000e8-0x00000000000000ef]\n  RIP: 0010:bpf_prog_test_run_xdp+0x52c/0x1700\n  Call Trace:\n   __sys_bpf+0x1662/0x50c0\n   __x64_sys_bpf+0x73/0xb0\n   do_syscall_64+0xf9/0x540\n   entry_SYSCALL_64_after_hwframe+0x77/0x7f\n  Kernel panic - not syncing: Fatal exception\n\nSnapshot every input field of opts with READ_ONCE() before validating or\nusing it.  The netns_id snapshot keeps the namespace get/put pair\nbalanced, while the other snapshots keep the remaining options from\nchanging partway through an invocation.  The individual reads can still\nobserve an inconsistent combination during a concurrent update, but each\nselected field value remains stable for that invocation."
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "baseScore": 7.8,
                "baseSeverity": "HIGH",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "scenarios": [
                {
                  "lang": "en",
                  "value": "AV:L - The bug is in BPF conntrack kfuncs reached only via the bpf() syscall (load, BPF_PROG_TEST_RUN, or attached XDP/TC programs), not from remote packet handling alone; kernel guidance classifies BPF as Local.\nAC:L - Exploitation needs a race on opts-\u003enetns_id in a shared BPF map value, but the attacker authors the program, drives concurrent bpf_map_update_elem and kfunc calls, and can pin threads to different CPUs to win the race reliably.\nPR:L - Triggering bpf_xdp_ct_lookup/bpf_skb_ct_lookup requires loading XDP or TC-BPF programs, which needs CAP_BPF and CAP_NET_ADMIN; both are obtainable by an unprivileged user inside a user/network namespace via unshare.\nUI:N - No victim interaction is required; the attacker loads their own BPF program, supplies map-backed opts, and runs concurrent test-run or traffic to trigger the refcount imbalance themselves.\nS:U - Impact is premature destruction of a live network namespace and kernel crashes within the same kernel security domain; it does not cross a VM, container-to-host, or IOMMU boundary.\nC:H - Repeated unmatched put_net() can drop a live namespace refcount to zero and free it while still in use, creating a net-namespace use-after-free that can expose freed kernel memory and enable information disclosure.\nI:H - The refcount corruption can destroy active network namespaces and corrupt kernel networking state; such lifetime bugs are memory corruption primitives that can be leveraged for arbitrary kernel modification or control-flow hijacking.\nA:H - The fix commit documents a reproduced general protection fault and kernel panic in bpf_prog_test_run_xdp from a null-ptr-deref after the namespace is destroyed, confirming complete system availability loss."
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-10-15T10:09:22.663Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
          },
          "references": [
            {
              "url": "https://git.kernel.org/stable/c/4af94462c0ca2187a02a1a6641020ae888c74d5c"
            },
            {
              "url": "https://git.kernel.org/stable/c/e5e060eb63d10b41ab60fd955649479d99b38210"
            },
            {
              "url": "https://git.kernel.org/stable/c/fdeba03fea78407a8c52faa99177c9f7f29f90eb"
            }
          ],
          "title": "bpf: Fix netns reference imbalance in conntrack kfuncs",
          "x_generator": {
            "engine": "bippy-1.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2026-74715",
        "datePublished": "2026-08-22T15:33:10.262Z",
        "dateReserved": "2026-08-15T05:44:03.928Z",
        "dateUpdated": "2026-10-16T19:16:11.506Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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