CVE-2024-39536: Junos OS and Junos OS Evolved: Flaps of BFD sessions with authentication cause a ppmd memory leak

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 the Periodic Packet Management Daemon (ppmd) of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated adjacent attacker to cause a Denial-of-Service (DoS). When a BFD session configured with authentication flaps, ppmd memory can leak. Whether the leak happens depends on a race condition which is outside the attackers control. This issue only affects BFD operating in distributed aka delegated (which is the default behavior) or inline mode. Whether the leak occurs can be monitored with the following CLI command: > show ppm request-queue FPC Pending-request fpc0 2 request-total-pending: 2 where a continuously increasing number of pending requests is indicative of the leak. This issue affects: Junos OS: * All versions before 21.2R3-S8, * 21.4 versions before 21.4R3-S7, * 22.1 versions before 22.1R3-S4, * 22.2 versions before 22.2R3-S4, * 22.3 versions before 22.3R3, * 22.4 versions before 22.4R2-S2, 22.4R3. Junos OS Evolved: * All versions before 21.2R3-S8-EVO, * 21.4-EVO versions before 21.4R3-S7-EVO, * 22.2-EVO versions before 22.2R3-S4-EVO, * 22.3-EVO versions before 22.3R3-EVO, * 22.4-EVO versions before 22.4R3-EVO.

Affected products

Juniper Junos OS: before 21.2; 21.4, 21.4-r1, 21.4-r1-s1, 21.4-r1-s2, 21.4-r2, 21.4-r2-s1 (+44) — fixed in 21.2
Juniper Networks Junos OS Evolved: before 21.2; 21.2, 21.2-r1, 21.2-r1-s1, 21.2-r1-s2, 21.2-r2, 21.2-r2-s1 (+48) — fixed in 21.2

How to fix

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

References

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