CVE-2025-21591 — Junos OS: An unauthenticated adjacent attacker sending a malformed DHCP packet causes jdhcpd to crash

Affected: Juniper Networks Junos OS

A Buffer Access with Incorrect Length Value vulnerability in the jdhcpd daemon of Juniper Networks Junos OS, when DHCP snooping is enabled, allows an unauthenticated, adjacent, attacker to send a DHCP packet with a malformed DHCP option to cause jdhcp to crash creating a Denial of Service (DoS) condition.

Continuous receipt of these DHCP packets using the malformed DHCP Option will create a sustained Denial of Service (DoS) condition.

This issue affects Junos OS:

* from 23.1 before 23.2R2-S3, * from 23.4 before 23.4R2-S3, * from 24.2 before 24.2R2.

This issue isn't applicable to any versions of Junos OS before 23.1R1.

This issue doesn't affect vSRX Series which doesn't support DHCP Snooping.

This issue doesn't affect Junos OS Evolved.

There are no indicators of compromise for this issue.

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CVE-2025-21591 — Junos OS: An unauthenticated adjacent attacker sending a malformed DHCP packet causes jdhcpd to crash