CVE-2009-0635

Status: ModifiedHigh (7.1)—
Severity7.1High · CVSS 2.0
Exploitation probability2.51 %higher than 85% of CVEs
Active exploitationNonot in the CISA catalog
Public exploitNot knownno public code found

Memory leak in the Cisco Tunneling Control Protocol (cTCP) encapsulation feature in Cisco IOS 12.4, when an Easy VPN (aka EZVPN) server is enabled, allows remote attackers to cause a denial of service (memory consumption and device crash) via a sequence of TCP packets.

CVSS

Base score
7.1
Version
2.0
Vector
AV:N/AC:M/Au:N/C:N/I:N/A:C

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days
2.51 %
Percentile among all scored CVEs
85
Score date
10/23/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (1)

CWEs

References

Show 14 references

Raw JSON (NVD)

Show
{
  "id": "CVE-2009-0635",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 7.1,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:M/Au:N/C:N/I:N/A:C",
          "authentication": "NONE",
          "integrityImpact": "NONE",
          "accessComplexity": "MEDIUM",
          "availabilityImpact": "COMPLETE",
          "confidentialityImpact": "NONE"
        },
        "acInsufInfo": false,
        "impactScore": 6.9,
        "baseSeverity": "HIGH",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 8.6,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ]
  },
  "affected": [
    {
      "source": "psirt@cisco.com",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "n/a",
          "versions": [
            {
              "status": "affected",
              "version": "n/a"
            }
          ]
        }
      ]
    }
  ],
  "published": "2009-03-27T16:30:02.077",
  "references": [
    {
      "url": "http://secunia.com/advisories/34438",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "psirt@cisco.com"
    },
    {
      "url": "http://www.cisco.com/en/US/products/products_security_advisory09186a0080a90459.shtml",
      "tags": [
        "Patch",
        "Vendor Advisory"
      ],
      "source": "psirt@cisco.com"
    },
    {
      "url": "http://www.cisco.com/en/US/products/products_security_advisory09186a0080a90469.shtml",
      "tags": [
        "Patch",
        "Vendor Advisory"
      ],
      "source": "psirt@cisco.com"
    },
    {
      "url": "http://www.securityfocus.com/bid/34246",
      "source": "psirt@cisco.com"
    },
    {
      "url": "http://www.securitytracker.com/id?1021895",
      "source": "psirt@cisco.com"
    },
    {
      "url": "http://www.vupen.com/english/advisories/2009/0851",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "psirt@cisco.com"
    },
    {
      "url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/49417",
      "source": "psirt@cisco.com"
    },
    {
      "url": "http://secunia.com/advisories/34438",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "http://www.cisco.com/en/US/products/products_security_advisory09186a0080a90459.shtml",
      "tags": [
        "Patch",
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "http://www.cisco.com/en/US/products/products_security_advisory09186a0080a90469.shtml",
      "tags": [
        "Patch",
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "http://www.securityfocus.com/bid/34246",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "http://www.securitytracker.com/id?1021895",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "http://www.vupen.com/english/advisories/2009/0851",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/49417",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-399"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Memory leak in the Cisco Tunneling Control Protocol (cTCP) encapsulation feature in Cisco IOS 12.4, when an Easy VPN (aka EZVPN) server is enabled, allows remote attackers to cause a denial of service (memory consumption and device crash) via a sequence of TCP packets."
    },
    {
      "lang": "es",
      "value": "Perdida de memoria en la funcionalidad de encapsulado de Cisco Tunneling Control Protocol (cTCP) en Cisco IOS v12.4, cuando se ha habilitado un servidor Easy VPN (conocido como EZVPN), permite a atacantes remotos provocar una denegación de servicio (consumo de memoria y caída del dispositivo) mediante una secuencia de paquetes TCP."
    }
  ],
  "lastModified": "2026-06-16T23:05:27.873",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:cisco:ios:12.4t:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "BEAD7398-D1B2-47FB-952D-8C3162D5A363"
            },
            {
              "criteria": "cpe:2.3:o:cisco:ios:12.4xz:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "4963A243-74FA-43AD-9645-C9FAD527A6E1"
            },
            {
              "criteria": "cpe:2.3:o:cisco:ios:12.4ya:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "31C6EACA-35BE-4032-93DA-5F738AEE0F4A"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "psirt@cisco.com",
  "evaluatorSolution": "Per: http://www.cisco.com/en/US/products/products_security_advisory09186a0080a90469.shtml\r\n\r\n\r\nObtaining Fixed Software\r\n\r\nCisco has released free software updates that address these vulnerabilities. Prior to deploying software, customers should consult their maintenance provider or check the software for feature set compatibility and known issues specific to their environment.\r\n\r\nCustomers may only install and expect support for the feature sets they have purchased. By installing, downloading, accessing or otherwise using such software upgrades, customers agree to be bound by the terms of Cisco's software license terms found at http://www.cisco.com/en/US/docs/general/warranty/English/EU1KEN_.html , or as otherwise set forth at Cisco.com Downloads at http://www.cisco.com/public/sw-center/sw-usingswc.shtml ."
}