CVE-2021-25217

NameCVE-2021-25217
DescriptionIn 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.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)
ReferencesDLA-2674-1
NVD severitylow
Debian Bugs989157

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
isc-dhcp (PTS)stretch4.3.5-3+deb9u1vulnerable
stretch (security)4.3.5-3+deb9u2fixed
buster4.4.1-2+deb10u1fixed
bookworm, sid, bullseye4.4.1-2.3fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
isc-dhcpsourcestretch4.3.5-3+deb9u2DLA-2674-1
isc-dhcpsourcebuster4.4.1-2+deb10u1
isc-dhcpsource(unstable)4.4.1-2.3989157

Notes

https://kb.isc.org/docs/cve-2021-25217
https://www.openwall.com/lists/oss-security/2021/05/26/6
https://downloads.isc.org/isc/dhcp/4.4.2-P1/patches/4.4.2.CVE-2021-25217.patch

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