CVE-2026-21918

CVSS 7.5 HighEPSS 0.0%
  • CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  • Published: 2026-01-15T21:16:08.050

A Double Free vulnerability in the flow processing daemon (flowd) of Juniper Networks Junos OS on SRX and MX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). On all SRX and MX Series platforms, when during TCP session establishment a specific sequence of packets is encountered a double free happens. This causes flowd to crash and the respective FPC to restart.

This issue affects Junos OS on SRX and MX Series:

* all versions before 22.4R3-S7,
* 23.2 versions before 23.2R2-S3,
* 23.4 versions before 23.4R2-S4,
* 24.2 versions before 24.2R2.

Related CVE by CWE

No related CWE found.

Top CVE for Vendor

No vendor taxonomy on this entry.

Recently Exploited Similar Vulnerabilities

No recent KEV-listed items for this vendor/product.

How to fix CVE-2026-21918

CVE-2026-21918 is a high severity vulnerability affecting the affected product.

Description: A Double Free vulnerability in the flow processing daemon (flowd) of Juniper Networks Junos OS on SRX and MX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). On all SRX and MX Series platforms, when during TCP session establishment a specific sequence of packets is encountered a double free happens. This causes […]

Exploit Difficulty: EASY
⏱️ Time to exploit: < 1 hour
🛠️ Required skills: Basic web security knowledge
💰 Public exploits: Likely available

How to Fix:

1 Identify affected systems

- Check if you're running the affected product

2 Immediate actions

- Update to the latest patched version
- If patching is not immediately possible: restrict network exposure, apply least-privilege access

3 Verification

- Test the fix in a staging environment first
- Review logs for signs of exploitation
- Monitor for IOCs (Indicators of Compromise)

4 Long-term prevention

- Enable automatic security updates
- Set up vulnerability monitoring
- Review and harden security configurations

Exploit Difficulty Assessment

EASY
⏱️ Time to Exploit: < 1 hour
🛠️ Skills Required: Basic web security knowledge
💰 Public Exploits: Likely available

Vulnerability Timeline

Jan 15, 2026
Vulnerability Published

CVE details first published to NVD database

Jan 15, 2026
Imported to Database

Added to this CVE tracking system

Detection Rules & IOCs

No specific detection rules generated for this vulnerability type.

No vendor/product data available.