{"vuid":"VU#395670","idnumber":"395670","name":"FreeBSD fails to limit number of TCP segments held in reassembly queue","keywords":["FreeBSD","DoS","denial of service","out-of-sequence","TCP segments","mbufs","reassembly queue"],"overview":"FreeBSD fails to limit the number of TCP segments held in a reassembly queue which could allow an attacker to exhaust all available memory buffers (mbufs) on the destination system resulting in a denial-of-service condition.","clean_desc":"The Transmission Control Protocol (TCP) is part of the TCP/IP protocol suite and designed to provide reliable and connection-oriented service. In order to provide reliable service, TCP is designed to process packets that are delivered out of order so that these packets can later be re-assembled to create the entire TCP segment. There is a vulnerability in the way FreeBSD handles out-of-sequence TCP segments. When network packets making up a TCP segment are received out-of-sequence, these packets are held in a reassembly queue on the destination system so that they can be re-ordered and re-assembled. By sending a large number of out-of-sequence TCP packets, an unauthenticated, remote attacker could exhaust all memory buffers (mbufs) on the destination system resulting in a denial-of-service condition.","impact":"An unauthenticated, remote attacker could exhaust all memory buffers (mbufs) on the destination system resulting in a denial-of-service condition.","resolution":"Upgrade\nAccording to FreeBSD: Upgrade to the FreeBSD stable branch (4-STABLE) or to the RELENG_5_2, RELENG_4_9, or RELENG_4_8 security branch dated after the correction date. Apply Patch According to FreeBSD: The following patch has been verified to apply to FreeBSD 4.x and 5.x\nsystems. a) Download the relevant patch from the location below, and verify the\ndetached PGP signature using your PGP utility. [FreeBSD 5.2] # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:04/tcp52.patch\n# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:04/tcp52.patch.asc [FreeBSD 4.8, 4.9] # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:04/tcp47.patch\n# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:04/tcp47.patch.asc b) Apply the patch. # cd /usr/src\n# patch < /path/to/patch c) Recompile your kernel as described in\n<URL:http://www.freebsd.org/handbook/kernelconfig.html> and reboot the\nsystem.","workarounds":"","sysaffected":"","thanks":"This vulnerability was reported by \niDEFENSE","author":"This document was written by Damon Morda.","public":["ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-04:04.tcp.asc","http://www.idefense.com/application/poi/display?id=78&type=vulnerabilities","https://ialert.idefense.com/KODetails.jhtml?irId=207650","http://www.ietf.org/rfc/rfc793.txt"],"cveids":["CVE-2004-0171"],"certadvisory":"","uscerttechnicalalert":null,"datecreated":"2004-02-25T14:06:37Z","publicdate":"2004-02-18T00:00:00Z","datefirstpublished":"2004-03-04T20:05:57Z","dateupdated":"2004-03-04T20:08:59Z","revision":26,"vrda_d1_directreport":"","vrda_d1_population":"","vrda_d1_impact":"","cam_widelyknown":"15","cam_exploitation":"0","cam_internetinfrastructure":"15","cam_population":"15","cam_impact":"3","cam_easeofexploitation":"15","cam_attackeraccessrequired":"18","cam_scorecurrent":"6.834375","cam_scorecurrentwidelyknown":"7.9734375","cam_scorecurrentwidelyknownexploited":"12.5296875","ipprotocol":"","cvss_accessvector":"","cvss_accesscomplexity":"","cvss_authentication":null,"cvss_confidentialityimpact":"","cvss_integrityimpact":"","cvss_availabilityimpact":"","cvss_exploitablity":null,"cvss_remediationlevel":"","cvss_reportconfidence":"","cvss_collateraldamagepotential":"","cvss_targetdistribution":"","cvss_securityrequirementscr":"","cvss_securityrequirementsir":"","cvss_securityrequirementsar":"","cvss_basescore":"","cvss_basevector":"","cvss_temporalscore":"","cvss_environmentalscore":"","cvss_environmentalvector":"","metric":6.834375,"vulnote":null}