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No exploitation reportedFix available

CVE-2021-25217

No exploitation reported by the sources we read.

  • Published2021-05-26
  • WeaknessCWE-119

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2021-05-2622:15CVE publishedNVD

Versions per branch

NVD
Fedoraproject fedora
BranchAffectedFixed in
33.x= 33no fix published
34.x= 34no fix published
Isc dhcp
BranchAffectedFixed in
4.4≥ 4.4.0, ≤ 4.4.2no fix published
4.1= 4.1-esvno fix published
Siemens sinec ins
BranchAffectedFixed in
1.0< 1.01.0
1.0= 1.0no fix published

13 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • cri-oRed Hat:openshift:4.7::el8all versions · fixed in 0:1.20.3-6.rhaos4.7.git0d0f863.el8and 2 other packages
  • cri-oRed Hat:openshift:4.7::el7all versions · fixed in 0:1.20.3-6.rhaos4.7.git0d0f863.el7and 1 other package
  • dhcpTuxCare:OracleLinux:6all versions · fixed in 12:4.1.1-64.P1.0.1.el6.cloudlinux.ol.elsand 3 other packages
  • dhcpTuxCare:CentOS:6all versions · fixed in 12:4.1.1-64.P1.el6.cloudlinux.elsand 3 other packages
  • dhcpSUSE:OpenStack Cloud Crowbar 9all versions · fixed in 4.3.3-10.22.1
  • dhcpSUSE:OpenStack Cloud Crowbar 8all versions · fixed in 4.3.3-10.22.1
  • dhcpSUSE:OpenStack Cloud 9all versions · fixed in 4.3.3-10.22.1
  • dhcpSUSE:OpenStack Cloud 8all versions · fixed in 4.3.3-10.22.1

79 more package ranges on OSV.dev

Vendor advisories

  • CVE-2021-25217 Red Hat Product Security447 products fixed

    dhcp: stack-based buffer overflow when parsing statements with colon-separated hex digits in config or lease files in dhcpd and dhclient

  • ICSA-22-258-05 CISA1 known affected

    Siemens SINEC INS

    SINEC INS

  • SSA-637483 Siemens ProductCERT1 known affected

    SSA-637483 Third-Party Component Vulnerabilities in SINEC INS before V1.0 SP2

    SINEC INS

  • SSA-406691 Siemens ProductCERT10 known affected

    SSA-406691: Buffer Vulnerabilities in DHCP function of RUGGEDCOM ROX products

    RUGGEDCOM ROX MX5000 · RUGGEDCOM ROX RX1400 · RUGGEDCOM ROX RX1500 · +7 more

  • RHSA-2021:2555 Red Hat Product Security42 products fixed

    Red Hat Security Advisory: OpenShift Container Platform 4.7.19 packages and security update

  • RHSA-2021:2519 Red Hat Product Security4 products fixed

    Red Hat Security Advisory: RHV-H security update (redhat-virtualization-host) 4.3.16

10 more advisories

Full record on NVD

Fix

  1. Vendor fix Siemens ProductCERT SSA-637483 · 1 productUpdate to V1.0 SP2 or later version
  2. Vendor fix CISA ICSA-22-258-05 · 1 productUpdate to V1.0 SP2 or later version
  3. Vendor fix Siemens ProductCERT SSA-406691 · 10 productsUpdate to V2.15.0 or later version
  4. Vendor fix Red Hat Product Security RHSA-2021:2555 · 42 productsFor OpenShift Container Platform 4.7 see the following documentation, which will be updated shortly for this release, for important instructions on how to upgrade your cluster and fully apply this asynchronous errata update: https://docs.openshift.com/container-platform/4.7/release_notes/ocp-4-7-r…
  5. Vendor fix Red Hat Product Security RHSA-2021:2519 · 4 productsBefore applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/2974891
  6. Vendor fix Red Hat Product Security RHSA-2021:2469 · 43 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • CNACVSS 3.17.4known since 2026-10-23
  • NVDCVSS 3.17.4read 2026-10-23
  • NVDCVSS 2.03.3read 2026-10-23
  • NVDweakness (CWE)CWE-119read 2026-10-23
  • FIRST EPSSEPSS score6.1 %2026-11-08
  • OSVaffected packages—
  • GitHub Advisoriesadvisory—

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Published
2021-05-26
Last Modified
2026-06-17
NVD status
Modified
GitHub Advisory
GHSA-pf98-cx5w-r49r

Frequently asked questions

What is CVE-2021-25217?

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.

Is CVE-2021-25217 actively exploited?

Active exploitation of CVE-2021-25217 has not been confirmed. Its EPSS score was 6.1% on 2026-11-08, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-25217?

CVE-2021-25217 has a CVSS v3 base score of 7.4 (HIGH severity), with vector string CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H.

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