What’s Vulnerable › Vulnerabilities

CVE-2024-39540: Junos OS: SRX Series, and MX Series with SPC3: Specific valid TCP traffic can cause a pfe crash

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% 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-754

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 products

• Juniper Junos OS: 21.2-r3-s5

References

• https://supportportal.juniper.net/JSA83000
• https://supportportal.juniper.net/JSA83000

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