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 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.
The function fqdn_universe_decode() allocates buffer space for the contents of option 81 (fqdn) data received in a DHCP packet. The maximum length of a DNS label is 63 bytes. The function tests the length byte of each label contained in the fqdn; if it finds a label whose length byte value is larger than 63, it returns without dereferencing the buffer space. This will cause a memory leak. Affects In ISC DHCP 1.0 -> 4.4.3, ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16-P1
Type: text
CWE ID: N/A
Description: The function fqdn_universe_decode() allocates buffer space for the contents of option 81 (fqdn) data received in a DHCP packet. The maximum length of a DNS label is 63 bytes. The function tests the length byte of each label contained in the fqdn; if it finds a label whose length byte value is larger than 63, it returns without dereferencing the buffer space. This will cause a memory leak. Affects In ISC DHCP 1.0 -> 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
As exploiting this vulnerability requires an attacker to send packets for an extended period of time, restarting servers periodically could be a viable workaround.
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.
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.