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.