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CVE-2021-0240

Junos OS: Receipt of malformed DHCPv6 packets causes jdhcpd to crash and restart.

High7.4EPSS 0.40%
Published
Updated
Reserved
Assigned by
juniper

Description

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.

Scores

CVSS scores of CVE-2021-0240, by who scored it
Scored byCVSSScoreVector
juniperCNA (assigner)3.1High7.4CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
NVDNVD · Modified3.1Medium6.5CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS (exploitation in 30 days)
0.40% · top 66% of all CVEs (7 Nov 2026)
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.4.

Weakness

Affected products

  • Juniper Networks · Junos OS

    • affected 17.3 – < 17.3R3-S12
    • affected 17.4 – < 17.4R3-S5
    • affected 18.1 – < 18.1R3-S13
    • affected 18.2 – < 18.2R3-S8
    • affected 18.3 – < 18.3R3-S5
    • affected 18.4 – < 18.4R1-S8, 18.4R3-S7
    • affected 19.1 – < 19.1R3-S5
    • affected 19.2 – < 19.2R3-S2
    • affected 19.3 – < 19.3R3-S2
    • affected 19.4 – < 19.4R3-S2
    • affected 20.1 – < 20.1R3
    • affected 20.2 – < 20.2R2-S3, 20.2R3
    • affected 20.3 – < 20.3R2
    • affected 20.4 – < 20.4R2

What to do

Solution: The following software releases have been updated to resolve this specific issue: Junos OS 17.3R3-S12, 17.4R3-S5, 18.1R3-S13, 18.2R3-S8, 18.3R3-S5, 18.4R1-S8, 18.4R3-S7, 19.1R3-S5, 19.2R3-S2, 19.3R3-S2, 19.4R3-S2, 20.1R3, 20.2R2-S3, 20.2R3, 20.3R2, 20.4R2, 21.1R1, and all subsequent releases.

Workaround: There are no viable workarounds for this issue.

Exploitation: Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

References (1)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .