CVE-2024-39542: An Improper Validation of Syntactic Correctness of Input vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on MX Series...

Description

An Improper Validation of Syntactic Correctness of Input vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on MX Series with MPC10/11 or LC9600, MX304, and Junos OS Evolved on ACX Series and PTX Series allows an unauthenticated, network based attacker to cause a Denial-of-Service (DoS). This issue can occur in two scenarios: 1. If a device, which is configured with SFLOW and ECMP, receives specific valid transit traffic, which is subject to sampling, the packetio process crashes, which in turn leads to an evo-aftman crash and causes the FPC to stop working until it is restarted. (This scenario is only applicable to PTX but not to ACX or MX.) 2. If a device receives a malformed CFM packet on an interface configured with CFM, the packetio process crashes, which in turn leads to an evo-aftman crash and causes the FPC to stop working until it is restarted. Please note that the CVSS score is for the formally more severe issue 1. The CVSS score for scenario 2. is: 6.5 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) This issue affects Junos OS: * All versions before 21.2R3-S4, * 21.4 versions before 21.4R2, * 22.2 versions before 22.2R3-S2; Junos OS Evolved: * All versions before 21.2R3-S8-EVO, * 21.4 versions before 21.4R2-EVO.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS 4.0

8.7/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.47%

37.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-1286

Affected Software

Vendor	Product	Versions
Juniper	Junos	21.4
Juniper	Junos	22.2
Juniper	Junos Os Evolved	21.2
Juniper	Junos Os Evolved	21.4

References

https://supportportal.juniper.net/JSA83002Vendor Advisory
https://supportportal.juniper.net/JSA83002Vendor Advisory

Timeline

Published: Jul 11, 2024
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2024-39542?

An Improper Validation of Syntactic Correctness of Input vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on MX Series with MPC10/11 or LC9600, MX304, and Junos OS Evolved on ACX Series and PTX Series allows an unauthenticated, network based attacker to cause a Denial-of-Service (DoS). This issue can occur in two scenarios: 1. If a device, which is configured with SFLOW and ECMP, receives specific valid transit traffic, which is subject to sampling, the packetio process crashes, which in turn leads to an evo-aftman crash and causes the FPC to stop working until it is restarted. (This scenario is only applicable to PTX but not to ACX or MX.) 2. If a device receives a malformed CFM packet on an interface configured with CFM, the packetio process crashes, which in turn leads to an evo-aftman crash and causes the FPC to stop working until it is restarted. Please note that the CVSS score is for the formally more severe issue 1. The CVSS score for scenario 2. is: 6.5 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) This issue affects Junos OS: * All versions before 21.2R3-S4, * 21.4 versions before 21.4R2, * 22.2 versions before 22.2R3-S2; Junos OS Evolved: * All versions before 21.2R3-S8-EVO, * 21.4 versions before 21.4R2-EVO.

How severe is CVE-2024-39542?

CVE-2024-39542 has a CVSS score of 8.7/10 (HIGH severity). The EPSS model estimates a 0.47% probability of exploitation in the next 30 days.

How do I fix CVE-2024-39542?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.