CVE-2025-21591: junos — Fix

Description

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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CVSS v3.1 Score

7.4

HIGH

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Weakness Type (CWE)

CWE-805 CWE-805

Affected Products

Vendor	Product	Versions
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All
juniper	junos	All

References

Advisories & Patches

https://supportportal.juniper.net/JSA96448

Frequently Asked Questions

What is CVE-2025-21591? +

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. It has a CVSS v3.1 base score of 7.4 (HIGH).

How severe is CVE-2025-21591? +

CVE-2025-21591 has a CVSS v3.1 score of 7.4 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-21591? +

CVE-2025-21591 affects products from juniper, specifically: junos. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-21591? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2025-21591