CVE-2024-39561
Junos OS: SRX4600, SRX5000 Series: TCP packets with SYN/FIN or SYN/RST are transferred after enabling no-syn-check with Express Path
An Improper Check for Unusual or Exceptional Conditions vulnerability in the flow daemon (flowd) of Juniper Networks Junos OS on
SRX4600 and SRX5000 Series
allows an attacker to send TCP packets with
SYN/FIN or SYN/RST
flags, bypassing the expected blocking of these packets.
A TCP packet with SYN/FIN or SYN/RST should be dropped in flowd. However, when no-syn-check and Express Path are enabled, these TCP packets are unexpectedly transferred to the downstream network.
This issue affects Junos OS on SRX4600 and SRX5000 Series:
- All versions before 21.2R3-S8,
- from 21.4 before 21.4R3-S7,
- from 22.1 before 22.1R3-S6,
- from 22.2 before 22.2R3-S4,
- from 22.3 before 22.3R3-S3,
- from 22.4 before 22.4R3-S2,
- from 23.2 before 23.2R2,
- from 23.4 before 23.4R1-S1, 23.4R2.
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
- None
Exploit likelihood
What each source reports
CVE List Score used
Junos OS: SRX4600, SRX5000 Series: TCP packets with SYN/FIN or SYN/RST are transferred after enabling no-syn-check with Express Path
An Improper Check for Unusual or Exceptional Conditions vulnerability in the flow daemon (flowd) of Juniper Networks Junos OS on
SRX4600 and SRX5000 Series
allows an attacker to send TCP packets with
SYN/FIN or SYN/RST
flags, bypassing the expected blocking of these packets.
A TCP packet with SYN/FIN or SYN/RST should be dropped in flowd. However, when no-syn-check and Express Path are enabled, these TCP packets are unexpectedly transferred to the downstream network.
This issue affects Junos OS on SRX4600 and SRX5000 Series:
- All versions before 21.2R3-S8,
- from 21.4 before 21.4R3-S7,
- from 22.1 before 22.1R3-S6,
- from 22.2 before 22.2R3-S4,
- from 22.3 before 22.3R3-S3,
- from 22.4 before 22.4R3-S2,
- from 23.2 before 23.2R2,
- from 23.4 before 23.4R1-S1, 23.4R2.
- Record
CVE-2024-39561- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N - CVSS 3.1
- 5.8 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N - Weakness
- CWE-754
- Updated
- 2026-11-02
EUVDEUVD-2024-38087
An Improper Check for Unusual or Exceptional Conditions vulnerability in the flow daemon (flowd) of Juniper Networks Junos OS on
SRX4600 and SRX5000 Series
allows an attacker to send TCP packets with
SYN/FIN or SYN/RST
flags, bypassing the expected blocking of these packets.
A TCP packet with SYN/FIN or SYN/RST should be dropped in flowd. However, when no-syn-check and Express Path are enabled, these TCP packets are unexpectedly transferred to the downstream network.
This issue affects Junos OS on SRX4600 and SRX5000 Series:
- All versions before 21.2R3-S8,
- from 21.4 before 21.4R3-S7,
- from 22.1 before 22.1R3-S6,
- from 22.2 before 22.2R3-S4,
- from 22.3 before 22.3R3-S3,
- from 22.4 before 22.4R3-S2,
- from 23.2 before 23.2R2,
- from 23.4 before 23.4R1-S1, 23.4R2.
- Record
EUVD-2024-38087- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-xvm6-65jm-mc4g
An Improper Check for Unusual or Exceptional Conditions vulnerability in the flow daemon (flowd)...
An Improper Check for Unusual or Exceptional Conditions vulnerability in the flow daemon (flowd) of Juniper Networks Junos OS on
SRX4600 and SRX5000 Series
allows an attacker to send TCP packets with
SYN/FIN or SYN/RST
flags, bypassing the expected blocking of these packets.
A TCP packet with SYN/FIN or SYN/RST should be dropped in flowd. However, when no-syn-check and Express Path are enabled, these TCP packets are unexpectedly transferred to the downstream network.
This issue affects Junos OS on SRX4600 and SRX5000 Series:
- All versions before 21.2R3-S8,
- from 21.4 before 21.4R3-S7,
- from 22.1 before 22.1R3-S6,
- from 22.2 before 22.2R3-S4,
- from 22.3 before 22.3R3-S3,
- from 22.4 before 22.4R3-S2,
- from 23.2 before 23.2R2,
- from 23.4 before 23.4R1-S1, 23.4R2.
- Record
GHSA-xvm6-65jm-mc4g- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N/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
- 5.8 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N - Weakness
- CWE-754
- Updated
- 2026-11-02
NVD
An Improper Check for Unusual or Exceptional Conditions vulnerability in the flow daemon (flowd) of Juniper Networks Junos OS on
SRX4600 and SRX5000 Series
allows an attacker to send TCP packets with
SYN/FIN or SYN/RST
flags, bypassing the expected blocking of these packets.
A TCP packet with SYN/FIN or SYN/RST should be dropped in flowd. However, when no-syn-check and Express Path are enabled, these TCP packets are unexpectedly transferred to the downstream network.
This issue affects Junos OS on SRX4600 and SRX5000 Series:
- All versions before 21.2R3-S8,
- from 21.4 before 21.4R3-S7,
- from 22.1 before 22.1R3-S6,
- from 22.2 before 22.2R3-S4,
- from 22.3 before 22.3R3-S3,
- from 22.4 before 22.4R3-S2,
- from 23.2 before 23.2R2,
- from 23.4 before 23.4R1-S1, 23.4R2.
- Record
CVE-2024-39561- CVSS 4.0
- 6.9 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N/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
- 5.8 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N - 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-2024-39561 is a medium vulnerability (CVSS 6.9) in Juniper Junos, published July 10, 2024. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.31%, the 24th percentile. No source names a fixed version.