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CVE-2026-63913

Estado: Pendiente de análisisAlta (8.2)—

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

netfilter: conntrack: tcp: do not force CLOSE on invalid-seq RST without direction check

An unintended behavior in the TCP conntrack state machine allows a connection to be forced into the CLOSE state using an RST packet with an invalid sequence number.

Specifically, after a SYN packet is observed, an RST with an invalid SEQ can transition the conntrack entry to TCP_CONNTRACK_CLOSE, regardless of whether the RST corresponds to the expected reply direction. The relevant code path assumes the RST is a response to an outgoing SYN, but does not validate packet direction or ensure that a matching SYN was actually sent in the opposite direction.

Leer descripción completaMostrar menos

As a result, a crafted packet sequence consisting of a SYN followed by an invalid-sequence RST can prematurely terminate an active NAT entry. This makes connection teardown easier than intended.

So, tighten the state transition logic to ensure that RST-triggered CLOSE transitions only occur when the RST is a valid response to a previously observed SYN in the correct direction.

CVSS

Probabilidad de explotación (EPSS)

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.

Vector AV:N/AC:L/PR:N (red sin privilegios). RST malformado desactiva entradas NAT causando denegación de servicio de conexiones activas; el impacto es la interrupción, no corrupción ni fuga.

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 TrafficVulnerability ScanningPrivileged Account ManagementNetwork SegmentationLimit Access to Resource Over NetworkApplication 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 KernelAI

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-63913",
  "cveTags": [],
  "metrics": {
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 8.2,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H",
          "integrityImpact": "LOW",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 4.2,
        "exploitabilityScore": 3.9
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  "published": "2026-07-19T16:17:09.237",
  "references": [
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Awaiting Analysis",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: conntrack: tcp: do not force CLOSE on invalid-seq RST without direction check\n\nAn unintended behavior in the TCP conntrack state machine allows a\nconnection to be forced into the CLOSE state using an RST packet with an\ninvalid sequence number.\n\nSpecifically, after a SYN packet is observed, an RST with an invalid SEQ\ncan transition the conntrack entry to TCP_CONNTRACK_CLOSE, regardless of\nwhether the RST corresponds to the expected reply direction. The relevant\ncode path assumes the RST is a response to an outgoing SYN, but does not\nvalidate packet direction or ensure that a matching SYN was actually sent\nin the opposite direction.\n\nAs a result, a crafted packet sequence consisting of a SYN followed by an\ninvalid-sequence RST can prematurely terminate an active NAT entry. This\nmakes connection teardown easier than intended.\n\nSo, tighten the state transition logic to ensure that RST-triggered\nCLOSE transitions only occur when the RST is a valid response to a\npreviously observed SYN in the correct direction."
    }
  ],
  "lastModified": "2026-07-27T17:44:23.777",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}