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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| ISC | ISC DHCP | 4.1 ESV – < 4.1-ESV-R16-P1, 4.4 – < 4.4.2-P1 | 4.1-ESV-R16-P1 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 13 | isc-dhcp | 4.4.1-2.3 | — |
| Debian 12 | isc-dhcp | 4.4.1-2.3 | — |
| Debian 9 | isc-dhcp | 4.3.5-3+deb9u2 | DLA-2674-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | isc-dhcp | 4.4.1-2.1ubuntu5.20.04.2 | USN-4969-1 |
| Ubuntu 18.04 LTS | isc-dhcp | 4.3.5-3ubuntu7.3 | USN-4969-1 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 16.04 LTS | isc-dhcp | 4.3.3-5ubuntu12.10+esm1 | USN-4969-2 |
| Ubuntu Pro 14.04 LTS | isc-dhcp | 4.2.4-7ubuntu12.13+esm1 | USN-4969-2 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8 | dhcp +5 | 12:4.3.6-44.el8_4.1 | RHSA-2021:2359 |
| RHEL 7 | dhcp +4 | 12:4.2.5-83.el7_9.1 | RHSA-2021:2357 |
| RHEL 7 | redhat-virtualization-host +1 | 4.3.16-20210615.0.el7_9 | RHSA-2021:2519 |
Show 13 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8.2 EUS | dhcp +5 | 12:4.3.6-40.el8_2.2 | RHSA-2021:2420 |
| RHEL 8.1 EUS | dhcp +5 | 12:4.3.6-34.el8_1.2 | RHSA-2021:2416 |
| RHEL 7.7 EUS | dhcp +4 | 12:4.2.5-77.el7_7.1 | RHSA-2021:2405 |
| RHEL 7.6 TUS | dhcp +4 | 12:4.2.5-69.el7_6.1 | RHSA-2021:2469 |
| RHEL 7.6 E4S | dhcp +4 | 12:4.2.5-69.el7_6.1 | RHSA-2021:2469 |
| RHEL 7.6 AUS | dhcp +4 | 12:4.2.5-69.el7_6.1 | RHSA-2021:2469 |
| RHEL 7.4 TUS | dhcp +4 | 12:4.2.5-58.el7_4.5 | RHSA-2021:2414 |
| RHEL 7.4 E4S | dhcp +4 | 12:4.2.5-58.el7_4.5 | RHSA-2021:2414 |
| RHEL 7.4 AUS | dhcp +4 | 12:4.2.5-58.el7_4.5 | RHSA-2021:2414 |
| RHEL 7.3 AUS | dhcp +4 | 12:4.2.5-47.el7_3.2 | RHSA-2021:2415 |
| RHEL 7.2 AUS | dhcp +4 | 12:4.2.5-42.el7_2.2 | RHSA-2021:2418 |
| RHEL 6 ELS | dhcp +3 | 12:4.1.1-64.P1.el6_10 | RHSA-2021:2419 |
| Red Hat OpenShift 4 | cri-o | 1.20.3-6.rhaos4.7.git0d0f863.el7 | RHSA-2021:2555 |
| Red Hat OpenShift 4 | dhcp +3 | 12:4.3.6-41.el8_3.1 | RHSA-2021:2555 |
| Red Hat OpenShift 4 | openshift-clients +1 | 4.7.0-202106252127.p0.git.8b4b094.el7 | RHSA-2021:2555 |
| Red Hat OpenShift 4 | openshift-kuryr +4 | 4.7.0-202106232224.p0.git.c7654fb.el8 | RHSA-2021:2555 |
| Red Hat OpenShift 4 | polkit +1 | 0.115-11.el8_3.2 | RHSA-2021:2555 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 8 | dhcp | 2:4.3.6-44.el8_4.1 | RLSA-2021:2359 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP3 | dhcp | 4.3.6.P1-6.11.1 | SUSE-SU-2021:1841-1 |
| SLES 15 SP2 | dhcp | 4.3.6.P1-6.11.1 | SUSE-SU-2021:1841-1 |
| SLES 15 SP1 | dhcp | 4.3.6.P1-6.11.1 | SUSE-SU-2021:1841-1 |
| SLES 15 | dhcp | 4.3.6.P1-6.11.1 | SUSE-SU-2021:1841-1 |
| SLES 12 SP5 | dhcp | 4.3.3-10.22.1 | SUSE-SU-2021:1822-1 |
Show 21 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 12 SP4 | dhcp | 4.3.3-10.22.1 | SUSE-SU-2021:1822-1 |
| SLES 12 SP3 | dhcp | 4.3.3-10.22.1 | SUSE-SU-2021:1822-1 |
| SLES 12 SP2 | dhcp | 4.3.3-10.22.1 | SUSE-SU-2021:1822-1 |
| SLES 11 SP4 | dhcp | 4.2.4.P2-0.28.12.1 | SUSE-SU-2021:14740-1 |
| SLES for SAP 15 SP1 | dhcp | 4.3.6.P1-6.11.1 | SUSE-SU-2021:1841-1 |
| SLES for SAP 15 | dhcp | 4.3.6.P1-6.11.1 | SUSE-SU-2021:1841-1 |
| SLES for SAP 12 SP5 | dhcp | 4.3.3-10.22.1 | SUSE-SU-2021:1822-1 |
| SLES for SAP 12 SP4 | dhcp | 4.3.3-10.22.1 | SUSE-SU-2021:1822-1 |
| SLES for SAP 12 SP3 | dhcp | 4.3.3-10.22.1 | SUSE-SU-2021:1822-1 |
| SLE HPC 15 SP1 | dhcp | 4.3.6.P1-6.11.1 | SUSE-SU-2021:1841-1 |
| SLE HPC 15 | dhcp | 4.3.6.P1-6.11.1 | SUSE-SU-2021:1841-1 |
| SUSE OpenStack Cloud Crowbar 9 | dhcp | 4.3.3-10.22.1 | SUSE-SU-2021:1822-1 |
| SUSE OpenStack Cloud Crowbar 8 | dhcp | 4.3.3-10.22.1 | SUSE-SU-2021:1822-1 |
| SUSE OpenStack Cloud 9 | dhcp | 4.3.3-10.22.1 | SUSE-SU-2021:1822-1 |
| SUSE OpenStack Cloud 8 | dhcp | 4.3.3-10.22.1 | SUSE-SU-2021:1822-1 |
| SUSE Manager Server 4.0 | dhcp | 4.3.6.P1-6.11.1 | SUSE-SU-2021:1841-1 |
| SUSE Manager Retail Branch Server 4.0 | dhcp | 4.3.6.P1-6.11.1 | SUSE-SU-2021:1841-1 |
| SUSE Manager Proxy 4.0 | dhcp | 4.3.6.P1-6.11.1 | SUSE-SU-2021:1841-1 |
| SUSE Linux Enterprise Point of Sale 11 SP3 | dhcp | 4.2.4.P2-0.28.12.1 | SUSE-SU-2021:14740-1 |
| SUSE HPE Helion OpenStack 8 | dhcp | 4.3.3-10.22.1 | SUSE-SU-2021:1822-1 |
| SUSE Enterprise Storage 6 | dhcp | 4.3.6.P1-6.11.1 | SUSE-SU-2021:1841-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | dhcp | 4.4.2.P1-2.4 | openSUSE-SU-2024:10715-1 |
| openSUSE Leap 15.3 | dhcp | 4.3.6.P1-6.11.1 | openSUSE-SU-2021:1841-1 |
| openSUSE Leap 15.2 | dhcp | 4.3.6.P1-lp152.8.6.1 | openSUSE-SU-2021:0834-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.20 | dhcp | 4.4.2_p1-r0 | — |
| Alpine v3.19 | dhcp | 4.4.2_p1-r0 | — |
| Alpine v3.18 | dhcp | 4.4.2_p1-r0 | — |
| Alpine v3.17 | dhcp | 4.4.2_p1-r0 | — |
| Alpine v3.16 | dhcp | 4.4.2_p1-r0 | — |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.15 | dhcp | 4.4.2_p1-r0 | — |
| Alpine v3.14 | dhcp | 4.4.2_p1-r0 | — |
| Alpine v3.13 | dhcp | 4.4.2_p1-r0 | — |
| Alpine v3.12 | dhcp | 4.4.2_p1-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | dhcp +4 | 12:4.2.5-77.amzn2.1.3 | ALAS2-2021-1654 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 2 (CBL-Mariner) | dhcp | 4.4.2-4 | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 8 | dhcp-libs +4 | 12:4.3.6-44.el8_4.1 | ELSA-2021-2359 |
| Oracle Linux 7 | dhcp +4 | 12:4.2.5-83.0.1.el7_9.1 | ELSA-2021-2357 |
Advisories 32
- RHSA-2021:2519 Red Hat Security Advisory: RHV-H security update (redhat-virtualization-host) 4.3.16 Red Hat Security Advisories (RHSA) · Oct 15, 2026
- RHSA-2021:2555 Red Hat Security Advisory: OpenShift Container Platform 4.7.19 packages and security update Red Hat Security Advisories (RHSA) · Aug 7, 2026
- RHSA-2021:2469 Red Hat Security Advisory: dhcp security update Red Hat Security Advisories (RHSA) · Aug 7, 2026
- RHSA-2021:2419 Red Hat Security Advisory: dhcp security update Red Hat Security Advisories (RHSA) · Aug 7, 2026
- RHSA-2021:2420 Red Hat Security Advisory: dhcp security update Red Hat Security Advisories (RHSA) · Aug 7, 2026
- RHSA-2021:2416 Red Hat Security Advisory: dhcp security update Red Hat Security Advisories (RHSA) · Aug 7, 2026
- RHSA-2021:2418 Red Hat Security Advisory: dhcp security update Red Hat Security Advisories (RHSA) · Aug 7, 2026
- RHSA-2021:2415 Red Hat Security Advisory: dhcp security update Red Hat Security Advisories (RHSA) · Aug 7, 2026
- RHSA-2021:2405 Red Hat Security Advisory: dhcp security update Red Hat Security Advisories (RHSA) · Aug 7, 2026
- RHSA-2021:2414 Red Hat Security Advisory: dhcp security update Red Hat Security Advisories (RHSA) · Aug 7, 2026
- RHSA-2021:2359 Red Hat Security Advisory: dhcp security update Red Hat Security Advisories (RHSA) · Aug 7, 2026
- RHSA-2021:2357 Red Hat Security Advisory: dhcp security update Red Hat Security Advisories (RHSA) · Aug 7, 2026
- USN-4969-2 isc-dhcp vulnerability Ubuntu Security Notices (USN) · Jun 29, 2026
- USN-4969-1 isc-dhcp vulnerability Ubuntu Security Notices (USN) · Apr 22, 2026
- DLA-2674-1 isc-dhcp - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2021:2359 Important: dhcp security update Rocky Linux Security Advisories · Feb 4, 2026
- SUSE-SU-2021:1841-1 Security update for dhcp SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:1841-1 Security update for dhcp SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2021:14740-1 Security update for dhcp SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:10715-1 dhcp-4.4.2.P1-2.4 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2021:0834-1 Security update for dhcp SUSE / openSUSE Security Updates · Feb 4, 2026
- WID-SEC-2023-0063 Juniper Junos Space: Mehrere Schwachstellen BSI CERT-Bund (WID) · Oct 8, 2025
- SCA-2025-0011 Vulnerabilities affecting Endress+Hauser SSG-E210GC SICK PSIRT · Oct 2, 2025
- SCA-2025-0009 Vulnerabilities affecting SICK TDC-E210GC SICK PSIRT · Aug 1, 2025
- SUSE-SU-2021:1822-1 Security update for dhcp SUSE / openSUSE Security Updates · May 2, 2025
- WID-SEC-2023-1261 Internet Systems Consortium DHCP: Schwachstelle ermöglicht Denial of Service BSI CERT-Bund (WID) · May 21, 2023
- ICSA-22-258-05 Siemens SINEC INS CISA ICS & IT advisories · Sep 13, 2022
- SSA-637483 SSA-637483 Third-Party Component Vulnerabilities in SINEC INS before V1.0 SP2 Siemens ProductCERT · Sep 13, 2022
- SSA-406691 SSA-406691: Buffer Vulnerabilities in DHCP function of RUGGEDCOM ROX products Siemens ProductCERT · Mar 8, 2022
- ALAS2-2021-1654 Important: dhcp security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Jun 22, 2021
- ELSA-2021-2357 Important: dhcp security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · Jun 10, 2021
- ELSA-2021-2359 Important: dhcp security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Jun 10, 2021
References
- https://kb.isc.org/docs/cve-2021-25217
- [oss-security] 20210526 ISC has disclosed a vulnerability in ISC DHCP (CVE-2021-25217) mailing-list
- FEDORA-2021-08cdb4dc34 vendor-advisory
- [debian-lts-announce] 20210603 [SECURITY] [DLA 2674-1] isc-dhcp security update mailing-list
- FEDORA-2021-8ca8263bde vendor-advisory
- https://cert-portal.siemens.com/productcert/pdf/ssa-406691.pdf
- https://security.netapp.com/advisory/ntap-20220325-0011/
- https://cert-portal.siemens.com/productcert/pdf/ssa-637483.pdf
- GLSA-202305-22 vendor-advisory