CVE-2024-39540

Junos OS: SRX Series, and MX Series with SPC3: Specific valid TCP traffic can cause a pfe crash

HIGH

7.5

CVSS Score

Published: July 11, 2024 at 04:16 PM UTC

Updated: June 17, 2026 at 07:42 AM UTC

38 products affected across 2 vendorsJunosSRX5600SRX5800

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Severity

HIGH7.5

Exploit prediction

EPSS 0.5%

SSVC

No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Junos · Juniper Networks

95%

21.2 ≤ v < 21.2r3-s621.2R3-S5 ≤ v < 21.2R3-S621.2 21.2 r3-s5 21.2R3-S5

Affected range stops below 21.2R3-S6, so it looks safe — our inference, not a vendor statement

juniper-csrx (environment) · juniper-mx240 (environment) · juniper-mx480 (environment) · juniper-mx960 (environment) · juniper-srx100 (environment) · juniper-srx110 (environment) · juniper-srx1400 (environment) · juniper-srx1500 (environment) · juniper-srx1600 (environment) · juniper-srx210 (environment) · juniper-srx220 (environment) · juniper-srx2300 (environment) · juniper-srx240 (environment) · juniper-srx240h2 (environment) · juniper-srx240m (environment) · juniper-srx300 (environment) · juniper-srx320 (environment) · juniper-srx340 (environment) · juniper-srx3400 (environment) · juniper-srx345 (environment) · juniper-srx3600 (environment) · juniper-srx380 (environment) · juniper-srx4000 (environment) · juniper-srx4100 (environment) · juniper-srx4200 (environment) · juniper-srx4300 (environment) · juniper-srx4600 (environment) · juniper-srx4700 (environment) · juniper-srx5000 (environment) · juniper-srx5400 (environment) · juniper-srx550 (environment) · juniper-srx550-hm (environment) · juniper-srx550m (environment) · juniper-srx5600 (environment) · juniper-srx5800 (environment) · juniper-srx650 (environment) · juniper-vsrx (environment)

Csrx · Juniperdevice

80%

All versions

Mx240 · Juniperdevice

80%

All versions

Mx480 · Juniperdevice

80%

All versions

Mx960 · Juniperdevice

80%

All versions