CVE-2021-0240
Junos OS: Receipt of malformed DHCPv6 packets causes jdhcpd to crash and restart.
On Juniper Networks Junos OS platforms configured as DHCPv6 local server or DHCPv6 Relay Agent, the Juniper Networks Dynamic Host Configuration Protocol Daemon (JDHCPD) process might crash if a malformed DHCPv6 packet is received, resulting in a restart of the daemon. The daemon automatically restarts without intervention, but continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue only affects DHCPv6. DHCPv4 is not affected by this issue. This issue affects Juniper Networks Junos OS: 17.3 versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R3-S5; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R1-S8, 18.4R3-S7; 19.1 versions prior to 19.1R3-S5; 19.2 versions prior to 19.2R3-S2; 19.3 versions prior to 19.3R3-S2; 19.4 versions prior to 19.4R3-S2; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R2-S3, 20.2R3; 20.3 versions prior to 20.3R2; 20.4 versions prior to 20.4R2.
Attack profile
How easy it is to exploit
- Attack vector
- Adjacent network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Junos OS: Receipt of malformed DHCPv6 packets causes jdhcpd to crash and restart.
On Juniper Networks Junos OS platforms configured as DHCPv6 local server or DHCPv6 Relay Agent, the Juniper Networks Dynamic Host Configuration Protocol Daemon (JDHCPD) process might crash if a malformed DHCPv6 packet is received, resulting in a restart of the daemon. The daemon automatically restarts without intervention, but continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue only affects DHCPv6. DHCPv4 is not affected by this issue. This issue affects Juniper Networks Junos OS: 17.3 versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R3-S5; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R1-S8, 18.4R3-S7; 19.1 versions prior to 19.1R3-S5; 19.2 versions prior to 19.2R3-S2; 19.3 versions prior to 19.3R3-S2; 19.4 versions prior to 19.4R3-S2; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R2-S3, 20.2R3; 20.3 versions prior to 20.3R2; 20.4 versions prior to 20.4R2.
- Record
CVE-2021-0240- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H - Weakness
- CWE-703
- Updated
- 2026-11-02
EUVDEUVD-2021-2859
On Juniper Networks Junos OS platforms configured as DHCPv6 local server or DHCPv6 Relay Agent, the Juniper Networks Dynamic Host Configuration Protocol Daemon (JDHCPD) process might crash if a malformed DHCPv6 packet is received, resulting in a restart of the daemon. The daemon automatically restarts without intervention, but continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue only affects DHCPv6. DHCPv4 is not affected by this issue. This issue affects Juniper Networks Junos OS: 17.3 versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R3-S5; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R1-S8, 18.4R3-S7; 19.1 versions prior to 19.1R3-S5; 19.2 versions prior to 19.2R3-S2; 19.3 versions prior to 19.3R3-S2; 19.4 versions prior to 19.4R3-S2; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R2-S3, 20.2R3; 20.3 versions prior to 20.3R2; 20.4 versions prior to 20.4R2.
- Record
EUVD-2021-2859- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-pvc4-6v97-6f49 No score
On Juniper Networks Junos OS platforms configured as DHCPv6 local server or DHCPv6 Relay Agent,...
On Juniper Networks Junos OS platforms configured as DHCPv6 local server or DHCPv6 Relay Agent, the Juniper Networks Dynamic Host Configuration Protocol Daemon (JDHCPD) process might crash if a malformed DHCPv6 packet is received, resulting in a restart of the daemon. The daemon automatically restarts without intervention, but continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue only affects DHCPv6. DHCPv4 is not affected by this issue. This issue affects Juniper Networks Junos OS: 17.3 versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R3-S5; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R1-S8, 18.4R3-S7; 19.1 versions prior to 19.1R3-S5; 19.2 versions prior to 19.2R3-S2; 19.3 versions prior to 19.3R3-S2; 19.4 versions prior to 19.4R3-S2; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R2-S3, 20.2R3; 20.3 versions prior to 20.3R2; 20.4 versions prior to 20.4R2.
- Record
GHSA-pvc4-6v97-6f49- Weakness
- CWE-755
- Updated
- 2026-11-02
NVD
On Juniper Networks Junos OS platforms configured as DHCPv6 local server or DHCPv6 Relay Agent, the Juniper Networks Dynamic Host Configuration Protocol Daemon (JDHCPD) process might crash if a malformed DHCPv6 packet is received, resulting in a restart of the daemon. The daemon automatically restarts without intervention, but continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue only affects DHCPv6. DHCPv4 is not affected by this issue. This issue affects Juniper Networks Junos OS: 17.3 versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R3-S5; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R1-S8, 18.4R3-S7; 19.1 versions prior to 19.1R3-S5; 19.2 versions prior to 19.2R3-S2; 19.3 versions prior to 19.3R3-S2; 19.4 versions prior to 19.4R3-S2; 20.1 versions prior to 20.1R3; 20.2 versions prior to 20.2R2-S3, 20.2R3; 20.3 versions prior to 20.3R2; 20.4 versions prior to 20.4R2.
- Record
CVE-2021-0240- CVSS 3.1
- 7.4 High
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H - CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - CVSS 2.0
- 2.9 Low
AV:A/AC:M/Au:N/C:N/I:N/A:P - Weakness
- CWE-703, CWE-755
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, published | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-0240 is a high vulnerability (CVSS 7.4) in Juniper Junos, published April 22, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.40%, the 34th percentile. No source names a fixed version.