A buffer overrun in lease file parsing code can be used to exploit a common vulnerability shared by dhcpd and dhclient
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.
- BDU:2021-03707
- DLA-2674-1
- openSUSE-SU-2021:0834-1
- openSUSE-SU-2021:1841-1
- openSUSE-SU-2024:10715-1
- RHSA-2021:2357
- RHSA-2021:2359
- RHSA-2021:2405
- RHSA-2021:2414
- RHSA-2021:2415
- RHSA-2021:2416
- RHSA-2021:2418
- RHSA-2021:2419
- RHSA-2021:2420
- RHSA-2021:2469
- RHSA-2021:2519
- RHSA-2021:2555
- RLSA-2021:2359
- SUSE-SU-2021:14740-1
- SUSE-SU-2021:1822-1
- Published
- May 26, 2021
- Updated
- Jun 16, 2026
- EPSS
- 6.1% · 93th percentile
- CWE
- CWE-119
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Report tools
Action score
31
Monitor
Low priority for now.
- CVSS
- 29 / 40 · 7.4 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 2 / 30 · 6.1%
CNA vs NVD score
- NVD
- —
- CNA · isc
- 7.4
- NVD has not scored this yet; the score shown is the CNA’s.
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| isc | dhcp | cpe:2.3:a:isc:dhcp |
| fedoraproject | fedora | cpe:2.3:o:fedoraproject:fedora |
| debian | debian linux | cpe:2.3:o:debian:debian_linux |
| siemens | ruggedcom rox rx1400 firmware | cpe:2.3:o:siemens:ruggedcom_rox_rx1400_firmware |
| siemens | ruggedcom rox rx1400 | cpe:2.3:h:siemens:ruggedcom_rox_rx1400 |
| siemens | ruggedcom rox rx1500 firmware | cpe:2.3:o:siemens:ruggedcom_rox_rx1500_firmware |
| siemens | ruggedcom rox rx1500 | cpe:2.3:h:siemens:ruggedcom_rox_rx1500 |
| siemens | ruggedcom rox rx1501 firmware | cpe:2.3:o:siemens:ruggedcom_rox_rx1501_firmware |
| siemens | ruggedcom rox rx1501 | cpe:2.3:h:siemens:ruggedcom_rox_rx1501 |
| siemens | ruggedcom rox rx1510 firmware | cpe:2.3:o:siemens:ruggedcom_rox_rx1510_firmware |
| siemens | ruggedcom rox rx1510 | cpe:2.3:h:siemens:ruggedcom_rox_rx1510 |
| siemens | ruggedcom rox rx1511 firmware | cpe:2.3:o:siemens:ruggedcom_rox_rx1511_firmware |
and 14 more
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- debian debian linux9.0
- fedoraproject fedora33
- fedoraproject fedora34
- isc dhcp4.4.0 and later · up to 4.4.2 inclusive
- isc dhcp4.1-esv
- netapp ontap select deploy administration utilityall versions
- netapp solidfire & hci management nodeall versions
- siemens ruggedcom rox mx5000 firmware2.3.0 and later · before 2.15.0
- siemens ruggedcom rox rx1400 firmwarebefore 2.15.0
- siemens ruggedcom rox rx1500 firmware2.3.0 and later · before 2.15.0
- siemens ruggedcom rox rx1501 firmware2.3.0 and later · before 2.15.0
- siemens ruggedcom rox rx1510 firmware2.3.0 and later · before 2.15.0
- siemens ruggedcom rox rx1511 firmware2.3.0 and later · before 2.15.0
- siemens ruggedcom rox rx1512 firmware2.3.0 and later · before 2.15.0
- siemens ruggedcom rox rx1524 firmwarebefore 2.15.0
- siemens ruggedcom rox rx1536 firmwarebefore 2.15.0
- siemens ruggedcom rox rx5000 firmware2.3.0 and later · before 2.15.0
- siemens sinec insbefore 1.0
- siemens sinec ins1.0
Versions reported by the vendor
Affected version ranges reported by the assigning authority (isc). Independent of NVD's CPE analysis and usually ahead of it.
ISC ISC DHCP
- 4.1 ESV and later · before 4.1-ESV-R16-P1affected
- 4.4 and later · before 4.4.2-P1affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Alpine:v3.12 | dhcp | from 4.4.0 · before 4.4.2_p1-r0 | 4.4.2_p1-r0 |
| Debian:12 | isc-dhcp | before 4.4.1-2.3 | 4.4.1-2.3 |
| Debian:9 | isc-dhcp | before 4.3.5-3+deb9u2 | 4.3.5-3+deb9u2 |
| openSUSE:Leap 15.2 | dhcp | before 4.3.6.P1-lp152.8.6.1 | 4.3.6.P1-lp152.8.6.1 |
| openSUSE:Leap 15.3 | dhcp | before 4.3.6.P1-6.11.1 | 4.3.6.P1-6.11.1 |
| openSUSE:Tumbleweed | dhcp | before 4.4.2.P1-2.4 | 4.4.2.P1-2.4 |
| Red Hat:enterprise_linux:7::client | dhclient | before 12:4.2.5-83.el7_9.1 | 12:4.2.5-83.el7_9.1 |
| Red Hat:enterprise_linux:7::client | dhcp | before 12:4.2.5-83.el7_9.1 | 12:4.2.5-83.el7_9.1 |
| Red Hat:enterprise_linux:7::client | dhcp-common | before 12:4.2.5-83.el7_9.1 | 12:4.2.5-83.el7_9.1 |
| Red Hat:enterprise_linux:7::client | dhcp-debuginfo | before 12:4.2.5-83.el7_9.1 | 12:4.2.5-83.el7_9.1 |
| Red Hat:enterprise_linux:7::client | dhcp-devel | before 12:4.2.5-83.el7_9.1 | 12:4.2.5-83.el7_9.1 |
| Red Hat:enterprise_linux:7::client | dhcp-libs | before 12:4.2.5-83.el7_9.1 | 12:4.2.5-83.el7_9.1 |
| Red Hat:enterprise_linux:7::hypervisor | redhat-virtualization-host | before 0:4.3.16-20210615.0.el7_9 | 0:4.3.16-20210615.0.el7_9 |
| Red Hat:enterprise_linux:7::hypervisor | redhat-virtualization-host-image-update | before 0:4.3.16-20210615.0.el7_9 | 0:4.3.16-20210615.0.el7_9 |
| Red Hat:enterprise_linux:8::baseos | dhcp | before 12:4.3.6-44.el8_4.1 | 12:4.3.6-44.el8_4.1 |
| Red Hat:enterprise_linux:8::baseos | dhcp-client | before 12:4.3.6-44.el8_4.1 | 12:4.3.6-44.el8_4.1 |
| Red Hat:enterprise_linux:8::baseos | dhcp-client-debuginfo | before 12:4.3.6-44.el8_4.1 | 12:4.3.6-44.el8_4.1 |
| Red Hat:enterprise_linux:8::baseos | dhcp-common | before 12:4.3.6-44.el8_4.1 | 12:4.3.6-44.el8_4.1 |
| Red Hat:enterprise_linux:8::baseos | dhcp-debuginfo | before 12:4.3.6-44.el8_4.1 | 12:4.3.6-44.el8_4.1 |
| Red Hat:enterprise_linux:8::baseos | dhcp-debugsource | before 12:4.3.6-44.el8_4.1 | 12:4.3.6-44.el8_4.1 |
| Red Hat:enterprise_linux:8::baseos | dhcp-libs | before 12:4.3.6-44.el8_4.1 | 12:4.3.6-44.el8_4.1 |
| Red Hat:enterprise_linux:8::baseos | dhcp-libs-debuginfo | before 12:4.3.6-44.el8_4.1 | 12:4.3.6-44.el8_4.1 |
| Red Hat:enterprise_linux:8::baseos | dhcp-relay | before 12:4.3.6-44.el8_4.1 | 12:4.3.6-44.el8_4.1 |
| Red Hat:enterprise_linux:8::baseos | dhcp-relay-debuginfo | before 12:4.3.6-44.el8_4.1 | 12:4.3.6-44.el8_4.1 |
+94
Same product
isc: all recordsOther highest-scoring records for the same primary product.
- CVE-2011-0997dhclient in ISC DHCP 3.0.x through 4.2.x before 4.2.1-P1, 3.1-ESV before 3.1-ESV-R1, and 4.1-ESV before 4.1-ESV-R2 allows remote attackers t55Plan
- CVE-2017-3144Failure to properly clean up closed OMAPI connections can exhaust available sockets52Plan
- CVE-2015-8605ISC DHCP 4.x before 4.1-ESV-R12-P1, 4.2.x, and 4.3.x before 4.3.3-P1 allows remote attackers to cause a denial of service (application crash51Plan
- CVE-2009-0692Stack-based buffer overflow in the script_write_params method in client/dhclient.c in ISC DHCP dhclient 4.1 before 4.1.0p1, 4.0 before 4.0.148Plan
- CVE-2016-2774ISC DHCP 4.1.x before 4.1-ESV-R13 and 4.2.x and 4.3.x before 4.3.4 does not restrict the number of concurrent TCP sessions, which allows rem45Plan
- CVE-2011-2749The server in ISC DHCP 3.x and 4.x before 4.2.2, 3.1-ESV before 3.1-ESV-R3, and 4.1-ESV before 4.1-ESV-R3 allows remote attackers to cause a43Plan
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| alpine:dhcp | 4.4.2_p1-r0 · Alpine:v3.12 | Package registry (OSV) |
| debian:isc-dhcp | 4.4.1-2.3 · Debian:12 | Package registry (OSV) |
| opensuse:dhcp | 4.3.6.P1-lp152.8.6.1 · openSUSE:Leap 15.2 | Package registry (OSV) |
| red hat:dhclient | 12:4.2.5-83.el7_9.1 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:dhcp | 12:4.2.5-83.el7_9.1 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:dhcp-client | 12:4.3.6-44.el8_4.1 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:dhcp-client-debuginfo | 12:4.3.6-44.el8_4.1 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:dhcp-common | 12:4.2.5-83.el7_9.1 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:dhcp-debuginfo | 12:4.2.5-83.el7_9.1 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:dhcp-debugsource | 12:4.3.6-44.el8_4.1 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:dhcp-devel | 12:4.2.5-83.el7_9.1 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:dhcp-libs | 12:4.2.5-83.el7_9.1 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:dhcp-libs-debuginfo | 12:4.3.6-44.el8_4.1 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:dhcp-relay | 12:4.3.6-44.el8_4.1 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| red hat:dhcp-relay-debuginfo | 12:4.3.6-44.el8_4.1 · Red Hat:enterprise_linux:8::baseos | Package registry (OSV) |
| rocky linux:dhcp | 2:4.3.6-44.el8_4.1 · Rocky Linux:8 | Package registry (OSV) |
| suse:dhcp | 4.2.4.P2-0.28.12.1 · SUSE:Linux Enterprise Point of Sale 11 SP3 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
- Jon FranklinDell and Pawel Wieczorkiewicz from Amazon Web Services for (independently) reporting this vulnerability.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Someone on the same network segment can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- high · the service can be disrupted
Impact can extend beyond the vulnerable component (scope changes).
- Attack vector
- Adjacent
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- High
Weakness class (CWE)
CWE-119 · Improper Restriction of Operations within the Bounds of a Memory BufferCVSS vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- Buffer Overflow via Environment VariablesCAPEC-10likelihood: High · High
- Overflow BuffersCAPEC-100likelihood: High · Very High
- Buffer ManipulationCAPEC-123likelihood: High · Very High
- Client-side Injection-induced Buffer OverflowCAPEC-14likelihood: Medium · High
- Filter Failure through Buffer OverflowCAPEC-24likelihood: High · High
- MIME ConversionCAPEC-42likelihood: High · High
- Overflow Binary Resource FileCAPEC-44likelihood: High · Very High
- Buffer Overflow via Symbolic LinksCAPEC-45likelihood: High · High
ATT&CK techniques
—
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- www.openwall.com/lists/oss-security/2021/05/26/6
- cert-portal.siemens.com/productcert/pdf/ssa-406691.pdf
- cert-portal.siemens.com/productcert/pdf/ssa-637483.pdf
- lists.debian.org/debian-lts-announce/2021/06/msg00002.html
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5QI4DYC7J4BGHEW3NH4XHMWTHYC36UK4/
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Z2LB42JWIV4M4WDNXX5VGIP26FEYWKIF/
- security.gentoo.org/glsa/202305-22
- security.netapp.com/advisory/ntap-20220325-0011/
Vendor advisories and official records. Exploit/PoC links are deliberately left out.