Juniper fixes critical RCE in its SRX firewalls and EX switches (CVE-2024-21591)

Juniper Networks has fixed a critical pre-authentication remote code execution (RCE) vulnerability (CVE-2024-21591) in Junos OS on SRX firewalls and EX switches.


About CVE-2024-21591

CVE-2024-21591 is an out-of-bounds write vulnerability that could allow an unauthenticated, network-based threat actor to carry out a denial-of service (DoS) attack, an RCE attack, or gain root privileges on exposed devices.

“This issue is caused by use of an insecure function allowing an attacker to overwrite arbitrary memory,” Juniper Networks noted in the security advisory.

The vulnerability, discovered during external security research, affects the following Junos OS SRX Series and EX Series versions:

  • Junos OS versions earlier than 20.4R3-S9
  • Junos OS 21.2 versions earlier than 21.2R3-S7
  • Junos OS 21.3 versions earlier than 21.3R3-S5
  • Junos OS 21.4 versions earlier than 21.4R3-S5
  • Junos OS 22.1 versions earlier than 22.1R3-S4
  • Junos OS 22.2 versions earlier than 22.2R3-S3
  • Junos OS 22.3 versions earlier than 22.3R3-S2
  • Junos OS 22.4 versions earlier than 22.4R2-S2, 22.4R3

“Juniper SIRT is not aware of any malicious exploitation of this vulnerability,” the company said.

Patch now!

The company has addressed the vulnerability in Junos OS versions 20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S3, 22.3R3-S2, 22.4R2-S2, 22.4R3, 23.2R1-S1, 23.2R2, 23.4R1, and all subsequent releases.

Admins are urged to patch their Junos OS instances on SRX or EX devices immediately. If this is not possible, they are advised to disable the J-Web interface or allow access to only trusted hosts.

Vulnerable Juniper networking devices

Censys currently sees over 10,000 exposed J-Web interfaces online, predominantly in Asia (South Korea, Hong Kong, China) and the US, mostly running on standard HTTP ports: 443, 8080, and 80.

Attackers frequently exploit vulnerabilities in Juniper networking devices to gain unauthorized access to systems within various organizations, often those of federal significance.

In November, CISA warned about five vulnerabilities that have been chained together by threat actors to compromise Juniper networking devices.

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