Vulnerability-Lookup

GHSA-8QQV-VCF6-Q7HX

Vulnerability from github – Published: 2026-08-22 18:30 – Updated: 2026-08-25 06:31

Details

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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-74715"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-22T16:16:46Z",
    "severity": "HIGH"
  },
  "details": "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.",
  "id": "GHSA-8qqv-vcf6-q7hx",
  "modified": "2026-08-25T06:31:29Z",
  "published": "2026-08-22T18:30:30Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74715"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e5e060eb63d10b41ab60fd955649479d99b38210"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fdeba03fea78407a8c52faa99177c9f7f29f90eb"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

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

Vulnerability from cvelistv5 – Published: 2026-08-22 15:33 – Updated: 2026-08-25 05:41

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

Assigner

Linux mitre root

References

2 references

URL	Tags
https://git.kernel.org/stable/c/e5e060eb63d10b41a…
https://git.kernel.org/stable/c/fdeba03fea78407a8…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: aed8ee7feb44b6537af1e0b4f03365d42928be38 , < e5e060eb63d10b41ab60fd955649479d99b38210 (git) Affected: aed8ee7feb44b6537af1e0b4f03365d42928be38 , < fdeba03fea78407a8c52faa99177c9f7f29f90eb (git)
Linux	Linux	Affected: 6.0 Unaffected: 0 , < 6.0 (semver) Unaffected: 7.1.9 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/nf_conntrack_bpf.c"
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              "lessThan": "fdeba03fea78407a8c52faa99177c9f7f29f90eb",
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              "versionType": "git"
            }
          ]
        },
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          ],
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          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.0"
            },
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              "version": "0",
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            {
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              "status": "unaffected",
              "version": "7.1.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "versionStartIncluding": "6.0",
                  "vulnerable": true
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          "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."
        }
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            "baseSeverity": "HIGH",
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            "version": "3.1"
          },
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              "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": "2026-08-25T05:41:58.565Z",
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        {
          "url": "https://git.kernel.org/stable/c/fdeba03fea78407a8c52faa99177c9f7f29f90eb"
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      "title": "bpf: Fix netns reference imbalance in conntrack kfuncs",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74715",
    "datePublished": "2026-08-22T15:33:10.262Z",
    "dateReserved": "2026-08-15T05:44:03.928Z",
    "dateUpdated": "2026-08-25T05:41:58.565Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
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}

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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