In ISC DHCP 1.0 -> 4.4.3, ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16-P1 a system with access to a DHCP server, sending DHCP packets crafted to include fqdn labels longer than 63 bytes, could eventually cause the server to run out of memory.

In ISC DHCP 4.4.0 -> 4.4.3, ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16-P1, when the function optioncodehashlookup() is called from addoption(), it increases the option's refcount field. However, there is not a corresponding call to optiondereference() to decrement the refcount field. The function addoption() is only used in server responses to lease query packets. Each lease query response calls this function for several options, so eventually, the reference counters could overflow and cause the server to abort.

A flaw was found in the Dynamic Host Configuration Protocol (DHCP). There is a discrepancy between the code that handles encapsulated option information in leases transmitted "on the wire" and the code which reads and parses lease information after it has been written to disk storage. This flaw allows an attacker to deliberately cause a situation where dhcpd while running in DHCPv4 or DHCPv6 mode, or the dhclient attempts to read a stored lease that contains option information, to trigger a stack-based buffer overflow in the option parsing code for colon-separated hex digits values. The highest threat from this vulnerability is to data confidentiality and integrity as well as service availability.

Failure to properly bounds check a buffer used for processing DHCP options allows a malicious server (or an entity masquerading as a server) to cause a buffer overflow (and resulting crash) in dhclient by sending a response containing a specially constructed options section.

Versions of DHCP affected: 4.1.0 -> 4.1-ESV-R15, 4.2.0 -> 4.2.8, 4.3.0 -> 4.3.6, 4.4.0

A malicious client which is allowed to send very large amounts of traffic (billions of packets) to a DHCP server can eventually overflow a 32-bit reference counter, potentially causing dhcpd to crash.

Versions of DHCP affected: 4.1.0 -> 4.1-ESV-R15, 4.2.0 -> 4.2.8, 4.3.0 -> 4.3.6, 4.4.0

A vulnerability stemming from failure to properly clean up closed OMAPI connections can lead to exhaustion of the pool of socket descriptors available to the DHCP server. Affects ISC DHCP 4.1.0 to 4.1-ESV-R15, 4.2.0 to 4.2.8, 4.3.0 to 4.3.6. Older versions may also be affected but are well beyond their end-of-life (EOL). Releases prior to 4.1.0 have not been tested.

ISC DHCP 4.1.x before 4.1-ESV-R13 and 4.2.x and 4.3.x before 4.3.4 does not restrict the number of concurrent TCP sessions, which allows remote attackers to cause a denial of service (INSIST assertion failure or request-processing outage) by establishing many sessions.

ISC DHCP 4.x before 4.1-ESV-R12-P1, 4.2.x, and 4.3.x before 4.3.3-P1 allows remote attackers to cause a denial of service (application crash) via an invalid length field in a UDP IPv4 packet.

ISC DHCP 4.1.x before 4.1-ESV-R7 and 4.2.x before 4.2.4-P2 allows remote attackers to cause a denial of service (daemon crash) in opportunistic circumstances by establishing an IPv6 lease in an environment where the lease expiration time is later reduced.

Multiple memory leaks in ISC DHCP 4.1.x and 4.2.x before 4.2.4-P1 and 4.1-ESV before 4.1-ESV-R6 allow remote attackers to cause a denial of service (memory consumption) by sending many requests.

ISC DHCP 4.1.2 through 4.2.4 and 4.1-ESV before 4.1-ESV-R6 allows remote attackers to cause a denial of service (infinite loop and CPU consumption) via a malformed client identifier.

dhcpd in ISC DHCP 4.x before 4.2.3-P1 and 4.1-ESV before 4.1-ESV-R4 does not properly handle regular expressions in dhcpd.conf, which allows remote attackers to cause a denial of service (daemon crash) via a crafted request packet.

The server in ISC DHCP 3.x and 4.x before 4.2.2, 3.1-ESV before 3.1-ESV-R3, and 4.1-ESV before 4.1-ESV-R3 allows remote attackers to cause a denial of service (daemon exit) via a crafted BOOTP packet.

The server in ISC DHCP 3.x and 4.x before 4.2.2, 3.1-ESV before 3.1-ESV-R3, and 4.1-ESV before 4.1-ESV-R3 allows remote attackers to cause a denial of service (daemon exit) via a crafted DHCP packet.

dhclient in ISC DHCP 3.0.x through 4.2.x before 4.2.1-P1, 3.1-ESV before 3.1-ESV-R1, and 4.1-ESV before 4.1-ESV-R2 allows remote attackers to execute arbitrary commands via shell metacharacters in a hostname obtained from a DHCP message, as demonstrated by a hostname that is provided to dhclient-script.

ISC DHCP server 4.2 before 4.2.0-P2, when configured to use failover partnerships, allows remote attackers to cause a denial of service (communications-interrupted state and DHCP client service loss) by connecting to a port that is only intended for a failover peer, as demonstrated by a Nagios checktcp process check to TCP port 520.

Common Vulnerabilities and Exposures assigned an identifier CVE-2010-3611 to the following vulnerability:

Name: CVE-2010-3611 URL: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-3611 Assigned: 20100927 Reference: CONFIRM: http://www.isc.org/software/dhcp/advisories/cve-2010-3611 Reference: CERT-VN:VU#102047 Reference: URL: http://www.kb.cert.org/vuls/id/102047 Reference: BID:44615 Reference: URL: http://www.securityfocus.com/bid/44615 Reference: SECUNIA:42082 Reference: URL: http://secunia.com/advisories/42082 Reference: VUPEN:ADV-2010-2879 Reference: URL: http://www.vupen.com/english/advisories/2010/2879 Reference: XF:iscdhcp-relayforward-dos(62965) Reference: URL: http://xforce.iss.net/xforce/xfdb/62965

ISC DHCP server 4.0 before 4.0.2, 4.1 before 4.1.2, and 4.2 before 4.2.0-P1 allows remote attackers to cause a denial of service (crash) via a DHCPv6 packet containing a Relay-Forward message without an address in the Relay-Forward link-address field.

ISC DHCP 4.1 before 4.1.1-P1 and 4.0 before 4.0.2-P1 allows remote attackers to cause a denial of service (server exit) via a zero-length client ID.

dhcpd in ISC DHCP 3.0.4 and 3.1.1, when the dhcp-client-identifier and hardware ethernet configuration settings are both used, allows remote attackers to cause a denial of service (daemon crash) via unspecified requests.

Robert Vogelgesang reported that dhcpd init script as used in dhcp packages in Red Hat Enterprise Linux 3 does not create temporary files safely inside configtest() function. Temporary file created by the script has predictable name (using script's process id), allowing local attacker to perform a symlink attack. When init script is called with configtest, restart or reload argument, arbitrary file may be overwritten by the output of 'dhcpd -t' (dhcpd.conf syntax check).

Description from ISC's advisory:

Description:

ISC dhclient has a stack overflow vulnerability which makes it theoretically possible for a rogue DHCP server to execute arbitrary commands as root on the affected system through stack return subversion.

Impact:

While generating a subnet number from the server-supplied leased address and subnet-mask 'dhclient' copies the information into a field without verifying if the length of the information exceeds the length of the field.

Theoretically this allows a rogue DHCP server to execute arbitrary commands as root on the affected system through stack return subversion.

This attack has little to no risk for a client situated on a network that is well defended, whereas clients that are roaming to potentially hostile or ad-hoc networks can see this attack to pose a severe threat.

Factors complicating any attack would be:

1) The attacker would need to generate messages the client views as authentic.

One option is for the attacker to present itself as a suitable DHCPv4 server for a network, in essence operating as a rogue DHCPv4 server.

Another option would be to insert messages into the conversation between the client and the authentic DHCPv4 server. To do this the attacker needs to accurately guess the client's randomly chosen 16-bit transaction ID and insert the attack precisely between the client's request and the valid DHCPv4 server's reply.

Neither of these are likely on a well defended network but clients that are roaming may find them, especially the first, a severe threat.

2) The attacker would then need to develop their attack within a limited packet size.

Support for DHCPv4 total packet size may be limited from 576 octets through the link MTU size (no support for fragmentation) up to 64KB. Of this, the DHCPv4 option payload space is limited by the space taken up by the BOOTP header space, excepting the FILE and SNAME fields (which can be used in 'option overloading' to carry option contents, such as the subnet-mask).

ISC dhcpd is prone to denial of service attack (daemon crash) when DHCP client specifies large value for dhcp-max-message-size in the request.

Problem only occurs when dhcpd is configured to provide clients with very large amount of DHCP options. Such configurations seems very unlikely to exist in the real deployments.