CVE-2022-2929 DHCP memory leak

CVE: CVE-2022-2929

Document version: 2.0

Posting date: 5 October 2022

Program impacted: ISC DHCP

Versions affected:

ISC DHCP:

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

Severity: Medium

Exploitable:

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

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.

Impact:

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

CVSS Vector: AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

For more information on the Common Vulnerability Scoring System and to obtain your specific environmental score please visit: https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H&version=3.1

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.

Active exploits:

We are not aware of any active exploits.

Solution:

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

Acknowledgments:

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

Do you still have questions? Questions regarding this advisory should go to security-officer@isc.org. To report a new issue, please encrypt your message using security-officer@isc.org's PGP key which can be found here: https://www.isc.org/pgpkey/. If you are unable to use encrypted email, you may also report new issues at: https://www.isc.org/reportbug/.

Note:

ISC patches only currently supported versions. When possible we indicate EOL versions affected. (For current information on which versions are actively supported, please see https://www.isc.org/download/.)

ISC Security Vulnerability Disclosure Policy:

Details of our current security advisory policy and practice can be found in the ISC Software Defect and Security Vulnerability Disclosure Policy at https://kb.isc.org/docs/aa-00861.

The Knowledgebase article https://kb.isc.org/docs/cve-2022-2929 is the complete and official security advisory document.

Legal Disclaimer:

Internet Systems Consortium (ISC) is providing this notice on an "AS IS" basis. No warranty or guarantee of any kind is expressed in this notice and none should be implied. ISC expressly excludes and disclaims any warranties regarding this notice or materials referred to in this notice, including, without limitation, any implied warranty of merchantability, fitness for a particular purpose, absence of hidden defects, or of non-infringement. Your use or reliance on this notice or materials referred to in this notice is at your own risk. ISC may change this notice at any time. A stand-alone copy or paraphrase of the text of this document that omits the document URL is an uncontrolled copy. Uncontrolled copies may lack important information, be out of date, or contain factual errors.