CVE-2024-39540
Junos OS: SRX Series, and MX Series with SPC3: Specific valid TCP traffic can cause a pfe crash
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Junos OS: SRX Series, and MX Series with SPC3: Specific valid TCP traffic can cause a pfe crash
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.
- Record
CVE-2024-39540- CVSS 4.0
- 8.7 High
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 - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-754
- Updated
- 2026-11-02
EUVDEUVD-2024-38066
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.
- Record
EUVD-2024-38066- CVSS 4.0
- 8.7 High
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 - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-xwcp-g9fq-2mmp
An Improper Check for Unusual or Exceptional Conditions vulnerability in the Packet Forwarding...
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.
- Record
GHSA-xwcp-g9fq-2mmp- CVSS 4.0
- 8.7 High
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 - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-754
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2024-39540- CVSS 4.0
- 8.7 High
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 - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-754
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, published | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2024-39540 is a high vulnerability (CVSS 8.7) in Juniper Junos, published July 11, 2024. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.49%, the 42nd percentile. No source names a fixed version.