CVE-2024-39539: Junos OS: MX Series: Continuous subscriber logins will lead to a memory leak and eventually an FPC crash

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-07-11 · updated 2026-06-17
Weakness: CWE-401

Description

A Missing Release of Memory after Effective Lifetime vulnerability in Juniper Networks Junos OS on MX Series allows an unauthenticated adjacent attacker to cause a Denial-of-Service (DoS). In a subscriber management scenario continuous subscriber logins will trigger a memory leak and eventually lead to an FPC crash and restart. This issue affects Junos OS on MX Series: * All version before 21.2R3-S6, * 21.4 versions before 21.4R3-S6, * 22.1 versions before 22.1R3-S5, * 22.2 versions before 22.2R3-S3, * 22.3 versions before 22.3R3-S2, * 22.4 versions before 22.4R3, * 23.2 versions before 23.2R2.

Affected products

Juniper Junos OS: before 21.2; 21.2, 21.2-r1, 21.2-r1-s1, 21.2-r1-s2, 21.2-r2, 21.2-r2-s1 (+62) — fixed in 21.2

How to fix

Upgrade to a fixed version: Juniper Junos OS 21.2. Check the vendor advisory for mitigations.

References

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