CVE-2026-80668

Estado: RecibidaCrítica (9.8)—

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_conntrack_expect: use conntrack GC to reap expectations

This patch replaces the timer API by GC worker approach for expectations, as it already happened in many other subsystems.

Use the existing conntrack GC worker to iterate over the local list of expectations in the master conntrack to reap expired expectations. Check IPS_HELPER_BIT to run GC for expectations, set it on for nft_ct expectation which nevers sets it.

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Hold the expectation spinlock while iterating over the master conntrack expectation list to synchronize with nf_ct_remove_expectations(). This also performs runtime packet path garbage collection through the expectation insertion and lookup functions while walking over one of the chains of the global expectation hashtables. Unconfirmed conntrack entries are skipped since ct->ext can be reallocated and dying are skipped since those will be gone soon. Set on IPS_HELPER_BIT if the helper ct extension is added, then the new GC worker does not need to bump the ct refcount to check if the ct->ext helper is available.

This removes the extra bump on the refcount for expectation timers, this allows to remove several nf_ct_expect_put() calls after the unlink, after this update only refcount remains at 1 while on the expectation hashes.

This patch implicitly addresses a race with the existing timer API allowing an expectation to access a stale exp->master pointer which has been already released when expectation removal loses races with an expiring timer, ie. timer_del() reporting false.

Add a new NF_CT_EXPECT_DEAD flag to reap this expectation via GC. This is needed by nf_conntrack_unexpect_related() which is called in error paths to invalidate newly created expectations that has been added into the hashes. These expectactions cannot be inmediately released as GC or nf_ct_remove_expectations() could race to make it. On expectation insert, the runtime GC reaps stale expectations before checking the expectation limit set by policy.

Set current timestamp in nf_ct_expect_alloc(), then add the expectation policy timeout (or custom timeout specified added on top of this) to specify the expectation lifetime.

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Puntuación base: 9.8

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.55%
Percentil entre todas las CVEs puntuadas: 44
Fecha de la puntuación: 6/10/2026

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

ExplotaciónT1190 Exploit Public-Facing Applicationinitial access75 %
Impacto principalT1499.004 Application or System Exploitationimpact65 %

Vulnerabilidad remota en kernel Linux (AV:N, PR:N, UI:N) permitiendo denegación de servicio por race condition en gestión de expectativas de conntrack, con potencial corrupción de estado de conexiones.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Filter Network Traffic Vulnerability Scanning Privileged Account Management Network Segmentation Limit Access to Resource Over Network Application Isolation and Sandboxing

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Linux — Linux Kernel^AI

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-80668",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 9.8,
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "bffcaad9afdfe45d7fc777397d3b83c1e3ebffe5",
              "lessThan": "7ec786f4230c2a9b2eaf97a2d45368933b49d2b2",
              "versionType": "git"
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            {
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            {
              "status": "affected",
              "version": "5e1c1d22268ae710c238342c8030c21daf298168",
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            {
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            {
              "status": "affected",
              "version": "6.1.176",
              "lessThan": "6.2",
              "versionType": "semver"
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            {
              "status": "affected",
              "version": "6.6.143",
              "lessThan": "6.7",
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            {
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            {
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            {
              "status": "affected",
              "version": "6.19.14",
              "lessThan": "6.20",
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          ],
          "programFiles": [
            "include/net/netfilter/nf_conntrack_expect.h",
            "include/uapi/linux/netfilter/nf_conntrack_common.h",
            "net/netfilter/nf_conntrack_core.c",
            "net/netfilter/nf_conntrack_expect.c",
            "net/netfilter/nf_conntrack_h323_main.c",
            "net/netfilter/nf_conntrack_helper.c",
            "net/netfilter/nf_conntrack_netlink.c",
            "net/netfilter/nf_conntrack_sip.c",
            "net/netfilter/nft_ct.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.0"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "7.0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver",
              "lessThanOrEqual": "7.1.*"
            },
            {
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "include/net/netfilter/nf_conntrack_expect.h",
            "include/uapi/linux/netfilter/nf_conntrack_common.h",
            "net/netfilter/nf_conntrack_core.c",
            "net/netfilter/nf_conntrack_expect.c",
            "net/netfilter/nf_conntrack_h323_main.c",
            "net/netfilter/nf_conntrack_helper.c",
            "net/netfilter/nf_conntrack_netlink.c",
            "net/netfilter/nf_conntrack_sip.c",
            "net/netfilter/nft_ct.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-08-28T08:16:52.080",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/7ec786f4230c2a9b2eaf97a2d45368933b49d2b2",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/b8b09dc2bf35a00d4e0556b5d6308c7b917ebda2",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack_expect: use conntrack GC to reap expectations\n\nThis patch replaces the timer API by GC worker approach for\nexpectations, as it already happened in many other subsystems.\n\nUse the existing conntrack GC worker to iterate over the local list of\nexpectations in the master conntrack to reap expired expectations.\nCheck IPS_HELPER_BIT to run GC for expectations, set it on for nft_ct\nexpectation which nevers sets it. Hold the expectation spinlock while\niterating over the master conntrack expectation list to synchronize with\nnf_ct_remove_expectations(). This also performs runtime packet path\ngarbage collection through the expectation insertion and lookup\nfunctions while walking over one of the chains of the global expectation\nhashtables. Unconfirmed conntrack entries are skipped since ct->ext can\nbe reallocated and dying are skipped since those will be gone soon.\nSet on IPS_HELPER_BIT if the helper ct extension is added, then the new\nGC worker does not need to bump the ct refcount to check if the ct->ext\nhelper is available.\n\nThis removes the extra bump on the refcount for expectation timers, this\nallows to remove several nf_ct_expect_put() calls after the unlink,\nafter this update only refcount remains at 1 while on the expectation\nhashes.\n\nThis patch implicitly addresses a race with the existing timer API\nallowing an expectation to access a stale exp->master pointer which has\nbeen already released when expectation removal loses races with an\nexpiring timer, ie. timer_del() reporting false.\n\nAdd a new NF_CT_EXPECT_DEAD flag to reap this expectation via GC. This\nis needed by nf_conntrack_unexpect_related() which is called in error\npaths to invalidate newly created expectations that has been added into\nthe hashes. These expectactions cannot be inmediately released as GC or\nnf_ct_remove_expectations() could race to make it. On expectation\ninsert, the runtime GC reaps stale expectations before checking the\nexpectation limit set by policy.\n\nSet current timestamp in nf_ct_expect_alloc(), then add the expectation\npolicy timeout (or custom timeout specified added on top of this) to\nspecify the expectation lifetime."
    }
  ],
  "lastModified": "2026-08-29T07:16:49.200",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}