In ISC DHCP 4.4.0 -> 4.4.3, ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16-P1, when the function option_code_hash_lookup() is called from add_option(), it increases the option's refcount field. However, there is not a corresponding call to option_dereference() to decrement the refcount field. The function add_option() 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.
4.1 ESV 4.1-ESV-R1 through versions before 4.1-ESV-R16-P1
Problem Types
Type
CWE ID
Description
text
N/A
A DHCP server configured with allow leasequery;, a remote machine with access to the server can send lease queries for the same lease multiple times, leading to the add_option() function being repeatedly called. This could cause an option's refcount field to overflow and the server to abort. Internally, reference counters are integers and thus overflow at 2^31 references, so even at 1000 lease query responses per second, it would take more than three weeks to crash the server. Affects In ISC DHCP 4.4.0 -> 4.4.3, ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16-P1
Type: text
CWE ID: N/A
Description: A DHCP server configured with allow leasequery;, a remote machine with access to the server can send lease queries for the same lease multiple times, leading to the add_option() function being repeatedly called. This could cause an option's refcount field to overflow and the server to abort. Internally, reference counters are integers and thus overflow at 2^31 references, so even at 1000 lease query responses per second, it would take more than three weeks to crash the server. Affects In ISC DHCP 4.4.0 -> 4.4.3, ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16-P1
Metrics
Version
Base score
Base severity
Vector
3.1
6.5
MEDIUM
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Version:3.1
Base score:6.5
Base severity: MEDIUM
Vector:
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Metrics Other Info
Impacts
CAPEC ID
Description
Solutions
Upgrade to the patched release most closely related to your current version of ISC DHCP. These can all be downloaded from https://www.isc.org/downloads. 4.4.3-P1 4.1-ESV-R16-P2
Configurations
Workarounds
Disable lease query on the server for DHCPv4 or restart the server periodically.
Exploits
We are not aware of any active exploits.
Credits
ISC would like to thank VictorV of Cyber Kunlun Lab for discovering and reporting this issue.