CVE-2021-25217 A buffer overrun in lease file parsing code can be used to exploit a common vulnerability shared by dhcpd and dhclient

What is CVE-2021-25217?

CVE-2021-25217 is a high-severity memory corruption vulnerability in Debian Debian Linux, published on 26 May 2021. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

In ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16, ISC DHCP 4.4.0 -> 4.4.2 (Other branches of ISC DHCP (i.e., releases in the 4.0.x series or lower and releases in the 4.3.x series) are beyond their End-of-Life (EOL) and no longer supported by ISC. From inspection it is clear that the defect is also present in releases from those series, but they have not been officially tested for the vulnerability), The outcome of encountering the defect while reading a lease that will trigger it varies, according to: the component being affected (i.e., dhclient or dhcpd) whether the package was built as a 32-bit or 64-bit binary whether the compiler flag -fstack-protection-strong was used when compiling In dhclient, ISC has not successfully reproduced the error on a 64-bit system. However, on a 32-bit system it is possible to cause dhclient to crash when reading an improper lease, which could cause network connectivity problems for an affected system due to the absence of a running DHCP client process. In dhcpd, when run in DHCPv4 or DHCPv6 mode: if the dhcpd server binary was built for a 32-bit architecture AND the -fstack-protection-strong flag was specified to the compiler, dhcpd may exit while parsing a lease file containing an objectionable lease, resulting in lack of service to clients. Additionally, the offending lease and the lease immediately following it in the lease database may be improperly deleted. if the dhcpd server binary was built for a 64-bit architecture OR if the -fstack-protection-strong compiler flag was NOT specified, the crash will not occur, but it is possible for the offending lease and the lease which immediately followed it to be improperly deleted.

Weakness: CWE-119

Which versions are affected by CVE-2021-25217?

It affects 16 products.

Products include Debian Debian Linux, Fedoraproject Fedora, Isc Dhcp, Netapp Ontap Select Deploy Administration Utility, Netapp Solidfire \& Hci Management Node, Siemens Ruggedcom Rox Mx5000 Firmware and 10 more.

How do I fix CVE-2021-25217?

Apply the vendor's patch.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2021-25217 being exploited?

There is no known exploitation of CVE-2021-25217 in the wild and no public exploit code.

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Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALPINE-CVE-2021-25217, AZL-6372, CLSA-2021-1623075541, CLSA-2021-1634922551, CLSA-2021-1635459208, DEBIAN-CVE-2021-25217 and 23 more.