rhsa-2001_142
Vulnerability from csaf_redhat
Published
2001-11-02 20:08
Modified
2024-11-21 22:12
Summary
Red Hat Security Advisory: kernel 2.2 and 2.4

Notes

Topic
Syncookies are used to protect a system against certain Denial Of Service (DOS) attacks. A flaw in this mechanism has been found which can be used to circumvent certain types of firewall configurations. Note: syncookies are not enabled in the default installation of Red Hat Linux but many server administrators do enable syncookies.
Details
Syncookies, while not enabled in default installations of Red Hat Linux, are used to protect an Internet server against a certain type of DoS attack--the so called "synflood"--by using a cryptographic challenge protocol which ensures legitimate users can keep using the server. Under an attack, the TCP/IP layer will, instead of just accepting new connections, send back the challenge and only accept the connections in the second phase ("syn ack") of the TCP/IP handshake (where the other party returns the challenge value). The DoS attack, which consists of sending as many first phase ("syn") packets as possible will be neutralized because system resources are only used as part of the second phase. Certain firewall configurations only filter the first phase ("syn") packets to prevent connections to specific services. These systems are vulnerable when an attacker can both force a system into flood protection state (by starting a synflood attack on a non-firewalled port) and guess the cryptographic challenge of a firewalled port. While the cryptographic hash used is strong, the number of bits available is restricted by the TCP protocol header design. With a high speed link and a lot of time, an attacker can eventually succeed in faking a valid cookie and making a connection that a syn only firewall rule might have prohibited. The updated kernels have a modified synflood protection algorithm that now uses a per port "under attack" state so that ports with only a first-phase firewall rule will not use the "under attack" regime even when other, non-firewalled, ports are under attack. In addition, these packages fix a remote denial of service attack against the TUX web server. This attack can only succeed if the TUX web server has been explicitly enabled; it is disabled by default. Thanks to Aidan O'Rawe for finding this bug.
Terms of Use
This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Red Hat Inc. and provide a link to the original.


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{
  "document": {
    "aggregate_severity": {
      "namespace": "https://access.redhat.com/security/updates/classification/",
      "text": "Important"
    },
    "category": "csaf_security_advisory",
    "csaf_version": "2.0",
    "distribution": {
      "text": "Copyright \u00a9 Red Hat, Inc. All rights reserved.",
      "tlp": {
        "label": "WHITE",
        "url": "https://www.first.org/tlp/"
      }
    },
    "lang": "en",
    "notes": [
      {
        "category": "summary",
        "text": "Syncookies are used to protect a system against certain Denial Of Service\n(DOS) attacks. A flaw in this mechanism has been found which can be used to\ncircumvent certain types of firewall configurations.\n\nNote: syncookies are not enabled in the default installation of Red Hat\nLinux but many server administrators do enable syncookies.",
        "title": "Topic"
      },
      {
        "category": "general",
        "text": "Syncookies, while not enabled in default installations of Red Hat Linux,\nare used to protect an Internet server against a certain type of DoS\nattack--the so called \"synflood\"--by using a cryptographic challenge\nprotocol which ensures legitimate users can keep using the server. Under an\nattack, the TCP/IP layer will, instead of just accepting new connections,\nsend back the challenge and only accept the connections in the\nsecond phase (\"syn ack\") of the TCP/IP handshake (where the other party\nreturns the challenge value). The DoS attack, which consists of sending as\nmany first phase (\"syn\") packets as possible will be neutralized because\nsystem resources are only used as part of the second phase.\n\nCertain firewall configurations only filter the first phase (\"syn\") packets\nto prevent connections to specific services. These systems are vulnerable\nwhen an attacker can both force a system into flood protection state (by\nstarting a synflood attack on a non-firewalled port) and guess the\ncryptographic challenge of a firewalled port. \n\nWhile the cryptographic hash used is strong, the number of bits available\nis restricted by the TCP protocol header design. With a high speed link and\na lot of time, an attacker can eventually succeed in faking a valid cookie\nand making a connection that a syn only firewall rule might have\nprohibited.\n\nThe updated kernels have a modified synflood protection algorithm that now\nuses a per port \"under attack\" state so that ports with only a first-phase\nfirewall rule will not use the \"under attack\" regime even when other,\nnon-firewalled, ports are under attack.\n\nIn addition, these packages fix a remote denial of service attack against\nthe TUX web server.  This attack can only succeed if the TUX web server\nhas been explicitly enabled; it is disabled by default.  Thanks to\nAidan O\u0027Rawe for finding this bug.",
        "title": "Details"
      },
      {
        "category": "legal_disclaimer",
        "text": "This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Red Hat Inc. and provide a link to the original.",
        "title": "Terms of Use"
      }
    ],
    "publisher": {
      "category": "vendor",
      "contact_details": "https://access.redhat.com/security/team/contact/",
      "issuing_authority": "Red Hat Product Security is responsible for vulnerability handling across all Red Hat products and services.",
      "name": "Red Hat Product Security",
      "namespace": "https://www.redhat.com"
    },
    "references": [
      {
        "category": "self",
        "summary": "https://access.redhat.com/errata/RHSA-2001:142",
        "url": "https://access.redhat.com/errata/RHSA-2001:142"
      },
      {
        "category": "external",
        "summary": "https://access.redhat.com/security/updates/classification/#important",
        "url": "https://access.redhat.com/security/updates/classification/#important"
      },
      {
        "category": "external",
        "summary": "http://cr.yp.to/syncookies.html",
        "url": "http://cr.yp.to/syncookies.html"
      },
      {
        "category": "external",
        "summary": "54829",
        "url": "https://bugzilla.redhat.com/show_bug.cgi?id=54829"
      },
      {
        "category": "external",
        "summary": "54851",
        "url": "https://bugzilla.redhat.com/show_bug.cgi?id=54851"
      },
      {
        "category": "external",
        "summary": "54868",
        "url": "https://bugzilla.redhat.com/show_bug.cgi?id=54868"
      },
      {
        "category": "external",
        "summary": "55067",
        "url": "https://bugzilla.redhat.com/show_bug.cgi?id=55067"
      },
      {
        "category": "external",
        "summary": "55082",
        "url": "https://bugzilla.redhat.com/show_bug.cgi?id=55082"
      },
      {
        "category": "external",
        "summary": "55097",
        "url": "https://bugzilla.redhat.com/show_bug.cgi?id=55097"
      },
      {
        "category": "self",
        "summary": "Canonical URL",
        "url": "https://security.access.redhat.com/data/csaf/v2/advisories/2001/rhsa-2001_142.json"
      }
    ],
    "title": "Red Hat Security Advisory: kernel 2.2 and 2.4",
    "tracking": {
      "current_release_date": "2024-11-21T22:12:12+00:00",
      "generator": {
        "date": "2024-11-21T22:12:12+00:00",
        "engine": {
          "name": "Red Hat SDEngine",
          "version": "4.2.1"
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      },
      "id": "RHSA-2001:142",
      "initial_release_date": "2001-11-02T20:08:00+00:00",
      "revision_history": [
        {
          "date": "2001-11-02T20:08:00+00:00",
          "number": "1",
          "summary": "Initial version"
        },
        {
          "date": "2001-10-26T00:00:00+00:00",
          "number": "2",
          "summary": "Last updated version"
        },
        {
          "date": "2024-11-21T22:12:12+00:00",
          "number": "3",
          "summary": "Last generated version"
        }
      ],
      "status": "final",
      "version": "3"
    }
  },
  "product_tree": {
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                "name": "Red Hat Linux 6.2",
                "product": {
                  "name": "Red Hat Linux 6.2",
                  "product_id": "Red Hat Linux 6.2",
                  "product_identification_helper": {
                    "cpe": "cpe:/o:redhat:linux:6.2"
                  }
                }
              },
              {
                "category": "product_name",
                "name": "Red Hat Linux 7.0",
                "product": {
                  "name": "Red Hat Linux 7.0",
                  "product_id": "Red Hat Linux 7.0",
                  "product_identification_helper": {
                    "cpe": "cpe:/o:redhat:linux:7.0"
                  }
                }
              },
              {
                "category": "product_name",
                "name": "Red Hat Linux 7.1",
                "product": {
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                  "product_id": "Red Hat Linux 7.1",
                  "product_identification_helper": {
                    "cpe": "cpe:/o:redhat:linux:7.1"
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                }
              },
              {
                "category": "product_name",
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                "product": {
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                  "product_id": "Red Hat Linux 7.2",
                  "product_identification_helper": {
                    "cpe": "cpe:/o:redhat:linux:7.2"
                  }
                }
              }
            ],
            "category": "product_family",
            "name": "Red Hat Linux"
          }
        ],
        "category": "vendor",
        "name": "Red Hat"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2001-0851",
      "ids": [
        {
          "system_name": "Red Hat Bugzilla ID",
          "text": "1616625"
        }
      ],
      "notes": [
        {
          "category": "description",
          "text": "Linux kernel 2.0, 2.2 and 2.4 with syncookies enabled allows remote attackers to bypass firewall rules by brute force guessing the cookie.",
          "title": "Vulnerability description"
        },
        {
          "category": "summary",
          "text": "security flaw",
          "title": "Vulnerability summary"
        }
      ],
      "product_status": {
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          "Red Hat Linux 7.0",
          "Red Hat Linux 7.1",
          "Red Hat Linux 7.2"
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          "summary": "Canonical URL",
          "url": "https://access.redhat.com/security/cve/CVE-2001-0851"
        },
        {
          "category": "external",
          "summary": "RHBZ#1616625",
          "url": "https://bugzilla.redhat.com/show_bug.cgi?id=1616625"
        },
        {
          "category": "external",
          "summary": "https://www.cve.org/CVERecord?id=CVE-2001-0851",
          "url": "https://www.cve.org/CVERecord?id=CVE-2001-0851"
        },
        {
          "category": "external",
          "summary": "https://nvd.nist.gov/vuln/detail/CVE-2001-0851",
          "url": "https://nvd.nist.gov/vuln/detail/CVE-2001-0851"
        }
      ],
      "release_date": "2001-11-02T00:00:00+00:00",
      "remediations": [
        {
          "category": "vendor_fix",
          "date": "2001-11-02T20:08:00+00:00",
          "details": "Before applying this update, make sure all previously released errata\nrelevant to your system have been applied. \n\nThe procedure for upgrading the kernel is documented at:\n\nhttp://www.redhat.com/support/docs/howto/kernel-upgrade/\n\nPlease read the directions for your architecture carefully before\nproceeding with the kernel upgrade.\n\nPlease note that this update is also available via Red Hat Network.  Many\npeople find this to be an easier way to apply updates.  To use Red Hat\nNetwork, launch the Red Hat Update Agent with the following command:\n\nup2date\n\nThis will start an interactive process that will result in the appropriate\nRPMs being upgraded on your system. Note that you need to select the kernel\nexplicitly on default configurations of up2date.",
          "product_ids": [
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            "Red Hat Linux 7.0",
            "Red Hat Linux 7.1",
            "Red Hat Linux 7.2"
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          "url": "https://access.redhat.com/errata/RHSA-2001:142"
        }
      ],
      "threats": [
        {
          "category": "impact",
          "details": "Important"
        }
      ],
      "title": "security flaw"
    },
    {
      "cve": "CVE-2001-0852",
      "ids": [
        {
          "system_name": "Red Hat Bugzilla ID",
          "text": "1616626"
        }
      ],
      "notes": [
        {
          "category": "description",
          "text": "TUX HTTP server 2.1.0-2 in Red Hat Linux allows remote attackers to cause a denial of service via a long Host: header.",
          "title": "Vulnerability description"
        },
        {
          "category": "summary",
          "text": "security flaw",
          "title": "Vulnerability summary"
        }
      ],
      "product_status": {
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          "url": "https://access.redhat.com/security/cve/CVE-2001-0852"
        },
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          "url": "https://bugzilla.redhat.com/show_bug.cgi?id=1616626"
        },
        {
          "category": "external",
          "summary": "https://www.cve.org/CVERecord?id=CVE-2001-0852",
          "url": "https://www.cve.org/CVERecord?id=CVE-2001-0852"
        },
        {
          "category": "external",
          "summary": "https://nvd.nist.gov/vuln/detail/CVE-2001-0852",
          "url": "https://nvd.nist.gov/vuln/detail/CVE-2001-0852"
        }
      ],
      "release_date": "2001-11-05T00:00:00+00:00",
      "remediations": [
        {
          "category": "vendor_fix",
          "date": "2001-11-02T20:08:00+00:00",
          "details": "Before applying this update, make sure all previously released errata\nrelevant to your system have been applied. \n\nThe procedure for upgrading the kernel is documented at:\n\nhttp://www.redhat.com/support/docs/howto/kernel-upgrade/\n\nPlease read the directions for your architecture carefully before\nproceeding with the kernel upgrade.\n\nPlease note that this update is also available via Red Hat Network.  Many\npeople find this to be an easier way to apply updates.  To use Red Hat\nNetwork, launch the Red Hat Update Agent with the following command:\n\nup2date\n\nThis will start an interactive process that will result in the appropriate\nRPMs being upgraded on your system. Note that you need to select the kernel\nexplicitly on default configurations of up2date.",
          "product_ids": [
            "Red Hat Linux 6.2",
            "Red Hat Linux 7.0",
            "Red Hat Linux 7.1",
            "Red Hat Linux 7.2"
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          "url": "https://access.redhat.com/errata/RHSA-2001:142"
        }
      ],
      "threats": [
        {
          "category": "impact",
          "details": "Important"
        }
      ],
      "title": "security flaw"
    }
  ]
}


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