A Double Free vulnerability in the flow processing daemon (flowd) of Juniper Networks Junos OS on SRX Series allows a network-based, unauthenticated attacker to cause a Denial of Service (DoS).

In a remote access VPN scenario, if a "tcp-encap-profile" is configured and a sequence of specific packets is received, a flowd crash and restart will be observed.

This issue affects Juniper Networks Junos OS:

• All versions earlier than 20.4R3-S8 on SRX Series;
• 21.2 versions earlier than 21.2R3-S6 on SRX Series;
• 21.3 versions earlier than 21.3R3-S5 on SRX Series;
• 21.4 versions earlier than 21.4R3-S5 on SRX Series;
• 22.1 versions earlier than 22.1R3-S3 on SRX Series;
• 22.2 versions earlier than 22.2R3-S3 on SRX Series;
• 22.3 versions earlier than 22.3R3-S1 on SRX Series;
• 22.4 versions earlier than 22.4R2-S2, 22.4R3 on SRX Series.

To be exposed to this issue the following configuration needs to be present:

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

This issue was seen during production usage.

This issue has been assigned CVE-2024-21606.

The following software releases have been updated to resolve this specific issue: 20.4R3-S8, 21.2R3-S6, 21.3R3-S5, 21.4R3-S5, 22.1R3-S3, 22.2R3-S3, 22.3R3-S1, 22.4R2-S2, 22.4R3*, 23.2R1, and all subsequent releases. (* pending publication)

This issue is being tracked as PR 1721936 which is visible on the Customer Support website.

Note: Juniper SIRT's policy is not to evaluate releases which are beyond End of Engineering (EOE) or End of Life (EOL).

2024-01-10: Initial Publication

• KB16613: Overview of the Juniper Networks SIRT Quarterly Security Bulletin Publication Process [juniper.net]
• KB16765: In which releases are vulnerabilities fixed? [juniper.net]
• KB16446: Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories [juniper.net]
• Report a Security Vulnerability - How to Contact the Juniper Networks Security Incident Response Team
• CVE-2024-21606 at cve.mitre.org