How severe is CVE-2024-39540?

CVE-2024-39540 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2024-39540 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2024-39540?

CVE-2024-39540 affects Juniper Junos. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2024-39540?

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-2024-39540 have an EU (EUVD) identifier?

Yes. CVE-2024-39540 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2024-38066.

When was CVE-2024-39540 published?

CVE-2024-39540 was published on 2024-07-11 and last updated on 2026-06-17.

CVE-2024-39540

CVE-2024-39540 is a high-severity vulnerability in Juniper Junos with a CVSS 3.x base score of 7.5. 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-754.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 8.7
EPSS exploit prediction: 0% (39th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2024-38066
Weakness: CWE-754
Affected product: Juniper Junos
Published: 2024-07-11
Last modified: 2026-06-17

Description

An Improper Check for Unusual or Exceptional Conditions vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS on SRX Series, and MX Series with SPC3 allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). When an affected device receives specific valid TCP traffic, the pfe crashes and restarts leading to a momentary but complete service outage. This issue affects Junos OS: 21.2 releases from 21.2R3-S5 before 21.2R3-S6. This issue does not affect earlier or later releases.

Frequently asked questions

What is CVE-2024-39540?: An Improper Check for Unusual or Exceptional Conditions vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS on SRX Series, and MX Series with SPC3 allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). When an affected device receives specific valid TCP traffic, the pfe crashes and restarts leading to a momentary but complete service outage. This issue affects Junos OS: 21.2 releases from 21.2R3-S5 before 21.2R3-S6. This issue does not affect earlier or later releases.
How severe is CVE-2024-39540?: CVE-2024-39540 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2024-39540 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2024-39540?: CVE-2024-39540 affects Juniper Junos. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2024-39540?: 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-2024-39540 have an EU (EUVD) identifier?: Yes. CVE-2024-39540 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2024-38066.
When was CVE-2024-39540 published?: CVE-2024-39540 was published on 2024-07-11 and last updated on 2026-06-17.

References

https://supportportal.juniper.net/JSA83000

Affected products (1)

cpe:2.3:o:juniper:junos:21.2:r3-s5:*:*:*:*:*:*

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