FKIE_CVE-2021-20177

Vulnerability from fkie_nvd - Published: 2021-05-26 21:15 - Updated: 2026-06-17 03:33
Severity
4.4 (Medium) - CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
Summary
A flaw was found in the Linux kernel's implementation of string matching within a packet. A privileged user (with root or CAP_NET_ADMIN) when inserting iptables rules could insert a rule which can panic the system. Kernel before kernel 5.5-rc1 is affected.
References
secalert@redhat.comhttps://bugzilla.redhat.com/show_bug.cgi?id=1914719Issue Tracking, Patch, Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108https://bugzilla.redhat.com/show_bug.cgi?id=1914719Issue Tracking, Patch, Third Party Advisory
Impacted products
Vendor Product Version
linux linux_kernel *
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "kernel",
          "vendor": "n/a",
          "versions": [
            {
              "status": "affected",
              "version": "kernel 5.5-rc1"
            }
          ]
        }
      ],
      "source": "secalert@redhat.com"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "A1E4152E-9A59-4E16-A122-CB88AFCEB7AF",
              "versionEndIncluding": "5.4.9",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "A flaw was found in the Linux kernel\u0027s implementation of string matching within a packet. A privileged user (with root or CAP_NET_ADMIN) when inserting iptables rules could insert a rule which can panic the system. Kernel before kernel 5.5-rc1 is affected."
    },
    {
      "lang": "es",
      "value": "Se encontr\u00f3 un fallo en la implementaci\u00f3n del kernel de Linux de la coincidencia de cadenas dentro de un paquete.\u0026#xa0;Un usuario privilegiado (con root o funci\u00f3n CAP_NET_ADMIN) cuando se insertan las reglas de iptables podr\u00eda insertar una regla que puede causar p\u00e1nico en el sistema.\u0026#xa0;El kernel anterior al kernel 5.5-rc1 est\u00e1 afectado"
    }
  ],
  "id": "CVE-2021-20177",
  "lastModified": "2026-06-17T03:33:25.347",
  "metrics": {
    "cvssMetricV2": [
      {
        "acInsufInfo": false,
        "baseSeverity": "LOW",
        "cvssData": {
          "accessComplexity": "LOW",
          "accessVector": "LOCAL",
          "authentication": "NONE",
          "availabilityImpact": "PARTIAL",
          "baseScore": 2.1,
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "vectorString": "AV:L/AC:L/Au:N/C:N/I:N/A:P",
          "version": "2.0"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 2.9,
        "obtainAllPrivilege": false,
        "obtainOtherPrivilege": false,
        "obtainUserPrivilege": false,
        "source": "nvd@nist.gov",
        "type": "Primary",
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 4.4,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "HIGH",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 0.8,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ]
  },
  "published": "2021-05-26T21:15:08.157",
  "references": [
    {
      "source": "secalert@redhat.com",
      "tags": [
        "Issue Tracking",
        "Patch",
        "Third Party Advisory"
      ],
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=1914719"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "tags": [
        "Issue Tracking",
        "Patch",
        "Third Party Advisory"
      ],
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=1914719"
    }
  ],
  "sourceIdentifier": "secalert@redhat.com",
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-125"
        }
      ],
      "source": "secalert@redhat.com",
      "type": "Secondary"
    }
  ]
}



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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

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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  • 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.



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.