CVE-2024-21599: MX Series: MPC3E memory leak with PTP configuration

Automatic summary from the vendor's CVE record. We haven't written a full analysis of this vulnerability yet.

Affected and fixed versions

Product / branch	Fixed in
Junos OS (MX Series) 0	20.4R3-S3 or later
Junos OS (MX Series) 21.1	21.1R3-S4 or later
Junos OS (MX Series) 21.2	21.2R3 or later
Junos OS (MX Series) 21.3	21.3R2-S1, 21.3R3 or later
Junos OS (MX Series) 21.4	21.4R2 or later
Junos OS (MX Series) 22.1	22.1R2 or later

Always confirm against the vendor advisory, which lists every fixed hotfix.

What it is

A Missing Release of Memory after Effective Lifetime vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on MX Series allows an adjacent, unauthenticated attacker to cause a Denial of Service (DoS).

If an MX Series device receives PTP packets on an MPC3E that doesn't support PTP this causes a memory leak which will result in unpredictable behavior and ultimately in an MPC crash and restart.

To monitor for this issue, please use the following FPC vty level commands:

show heap shows an increase in "LAN buffer" utilization and

show clksync ptp nbr-upd-info shows non-zero "Pending PFEs" counter.

This issue affects Juniper Networks Junos OS on MX Series with MPC3E:

All versions earlier than 20.4R3-S3;
21.1 versions earlier than 21.1R3-S4;
21.2 versions earlier than 21.2R3;
21.3 versions earlier than 21.3R2-S1, 21.3R3;
21.4 versions earlier than 21.4R2;
22.1 versions earlier than 22.1R2.

Am I affected?

To be affected by this issue an interface on the MPC needs to be configured with PTP as follows:

[ protocols ptp master/slave interface <interface-name> ]

Workarounds

Although not a workaround the leaked memory can be recovered by: deactivate protocol ptp; commit; activate protocol ptp; commit.

Exploitation

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

KEV status, EPSS score and vendor data refreshed automatically, last on 13 Oct 2026.