Vulnerability Database

346,508

Total vulnerabilities in the database

CVE-2024-39561 — juniper / junos

Improper Check for Unusual or Exceptional Conditions

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.
  • Published: Jul 10, 2024
  • Updated: Nov 16, 2025
  • CVE: CVE-2024-39561
  • Severity: Medium
  • Exploit:

CVSS v3:

  • Severity: Medium
  • Score: 5.8
  • AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

CWEs:

Software From Fixed in
juniper / junos - 21.2
juniper / junos 21.2-r3-s1 21.2-r3-s1.x
juniper / junos 21.2-r3-s2 21.2-r3-s2.x
juniper / junos 21.2-r3-s3 21.2-r3-s3.x
juniper / junos 21.2-r1 21.2-r1.x
juniper / junos 21.2-r1-s1 21.2-r1-s1.x
juniper / junos 21.2-r2 21.2-r2.x
juniper / junos 21.2 21.2.x
juniper / junos 21.2-r1-s2 21.2-r1-s2.x
juniper / junos 21.2-r2-s1 21.2-r2-s1.x
juniper / junos 21.2-r2-s2 21.2-r2-s2.x
juniper / junos 21.2-r3 21.2-r3.x
juniper / junos 21.2-r3-s4 21.2-r3-s4.x
juniper / junos 21.2-r3-s5 21.2-r3-s5.x
juniper / junos 21.2-r3-s6 21.2-r3-s6.x
juniper / junos 21.2-r3-s7 21.2-r3-s7.x
juniper / junos 21.4-r3-s4 21.4-r3-s4.x
juniper / junos 21.4-r3-s5 21.4-r3-s5.x
juniper / junos 21.4-r3-s6 21.4-r3-s6.x
juniper / junos 21.4 21.4.x
juniper / junos 21.4-r1 21.4-r1.x
juniper / junos 21.4-r1-s1 21.4-r1-s1.x
juniper / junos 21.4-r1-s2 21.4-r1-s2.x
juniper / junos 21.4-r2 21.4-r2.x
juniper / junos 21.4-r2-s1 21.4-r2-s1.x
juniper / junos 21.4-r3 21.4-r3.x
juniper / junos 21.4-r2-s2 21.4-r2-s2.x
juniper / junos 21.4-r3-s1 21.4-r3-s1.x
juniper / junos 21.4-r3-s2 21.4-r3-s2.x
juniper / junos 21.4-r3-s3 21.4-r3-s3.x
juniper / junos 22.1-r1-s2 22.1-r1-s2.x
juniper / junos 22.1-r2-s1 22.1-r2-s1.x
juniper / junos 22.1-r2-s2 22.1-r2-s2.x
juniper / junos 22.1-r3 22.1-r3.x
juniper / junos 22.1-r3-s1 22.1-r3-s1.x
juniper / junos 22.1-r3-s2 22.1-r3-s2.x
juniper / junos 22.1-r1 22.1-r1.x
juniper / junos 22.1-r1-s1 22.1-r1-s1.x
juniper / junos 22.1-r2 22.1-r2.x
juniper / junos 22.1 22.1.x
juniper / junos 22.1-r3-s3 22.1-r3-s3.x
juniper / junos 22.1-r3-s4 22.1-r3-s4.x
juniper / junos 22.1-r3-s5 22.1-r3-s5.x
juniper / junos 22.2 22.2.x
juniper / junos 22.2-r3 22.2-r3.x
juniper / junos 22.2-r3-s1 22.2-r3-s1.x
juniper / junos 22.2-r3-s2 22.2-r3-s2.x
juniper / junos 22.2-r3-s3 22.2-r3-s3.x
juniper / junos 22.2-r1 22.2-r1.x
juniper / junos 22.2-r1-s1 22.2-r1-s1.x
juniper / junos 22.2-r1-s2 22.2-r1-s2.x
juniper / junos 22.2-r2 22.2-r2.x
juniper / junos 22.2-r2-s1 22.2-r2-s1.x
juniper / junos 22.2-r2-s2 22.2-r2-s2.x
juniper / junos 22.3-r1 22.3-r1.x
juniper / junos 22.3-r1-s1 22.3-r1-s1.x
juniper / junos 22.3-r2 22.3-r2.x
juniper / junos 22.3 22.3.x
juniper / junos 22.3-r1-s2 22.3-r1-s2.x
juniper / junos 22.3-r2-s1 22.3-r2-s1.x
juniper / junos 22.3-r2-s2 22.3-r2-s2.x
juniper / junos 22.3-r3 22.3-r3.x
juniper / junos 22.3-r3-s1 22.3-r3-s1.x
juniper / junos 22.3-r3-s2 22.3-r3-s2.x
juniper / junos 22.4 22.4.x
juniper / junos 22.4-r1-s1 22.4-r1-s1.x
juniper / junos 22.4-r1-s2 22.4-r1-s2.x
juniper / junos 22.4-r2 22.4-r2.x
juniper / junos 22.4-r2-s1 22.4-r2-s1.x
juniper / junos 22.4-r2-s2 22.4-r2-s2.x
juniper / junos 22.4-r3 22.4-r3.x
juniper / junos 22.4-r3-s1 22.4-r3-s1.x
juniper / junos 22.4-r1 22.4-r1.x
juniper / junos 23.2 23.2.x
juniper / junos 23.2-r1 23.2-r1.x
juniper / junos 23.2-r1-s1 23.2-r1-s1.x
juniper / junos 23.2-r1-s2 23.2-r1-s2.x
juniper / junos 23.4 23.4.x
juniper / junos 23.4-r1 23.4-r1.x

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.