CVE-2022-2929 DHCP memory leak
  • 05 Oct 2022
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CVE-2022-2929 DHCP memory leak

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Article summary

CVE: CVE-2022-2929

Document version: 2.0

Posting date: 5 October 2022

Program impacted: ISC DHCP

Versions affected:


  • 1.0.0 -> 4.1-ESV-R16-P1
  • 4.2.0 -> 4.4.3.

Severity: Medium


From any adjacent networks from which an attacker can send requests to an ISC DHCP server.


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.


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.

CVSS Score: 6.5


For more information on the Common Vulnerability Scoring System and to obtain your specific environmental score please visit:


As exploiting this vulnerability requires an attacker to send packets for an extended period of time, restarting servers periodically could be a viable workaround.

Active exploits:

We are not aware of any active exploits.


Upgrade to the patched release most closely related to your current version of ISC DHCP. These can all be downloaded from

  • 4.4.3-P1
  • 4.1-ESV-R16-P2


ISC would like to thank VictorV of Cyber Kunlun Lab for discovering and reporting this issue.

Document revision history:

1.0 Early Notification, 28 September 2022
2.0 Public Disclosure, 5 October 2022

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ISC patches only currently supported versions. When possible we indicate EOL versions affected. (For current information on which versions are actively supported, please see

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Details of our current security advisory policy and practice can be found in the ISC Software Defect and Security Vulnerability Disclosure Policy at

The Knowledgebase article is the complete and official security advisory document.

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