How severe is CVE-2025-21591?

CVE-2025-21591 has a CVSS 3.x base score of 7.4, rated high severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2025-21591 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-21591?

CVE-2025-21591 primarily affects Juniper Junos. In total, 19 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2025-21591?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2025-21591 have an EU (EUVD) identifier?

Yes. CVE-2025-21591 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-10536.

When was CVE-2025-21591 published?

CVE-2025-21591 was published on 2025-04-09 and last updated on 2026-06-17.

CVE-2025-21591

CVE-2025-21591 is a high-severity vulnerability in Juniper Junos with a CVSS 3.x base score of 7.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-805.

Key facts

Severity: High (CVSS 3.x base score 7.4)
CVSS v4: 7.1
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-10536
Weakness: CWE-805
Affected product: Juniper Junos
Published: 2025-04-09
Last modified: 2026-06-17

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.

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.
How severe is CVE-2025-21591?: CVE-2025-21591 has a CVSS 3.x base score of 7.4, rated high severity. It is exploitable over an adjacent network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2025-21591 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-21591?: CVE-2025-21591 primarily affects Juniper Junos. In total, 19 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-21591?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2025-21591 have an EU (EUVD) identifier?: Yes. CVE-2025-21591 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-10536.
When was CVE-2025-21591 published?: CVE-2025-21591 was published on 2025-04-09 and last updated on 2026-06-17.

References

https://supportportal.juniper.net/JSA96448

Affected products (19)

cpe:2.3:o:juniper:junos:23.1:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:r2-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.2:r2-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:r1-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:r2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:r2-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:23.4:r2-s2:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:24.2:-:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:24.2:r1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:24.2:r1-s1:*:*:*:*:*:*
cpe:2.3:o:juniper:junos:24.2:r1-s2:*:*:*:*:*:*

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