Firewall filters bypass in Juniper Junos OS

1) Race condition

EUVDB-ID: #VU52284

Risk: Medium

CVSSv3.1: 4.9 [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-0247

CWE-ID: CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Exploit availability: No

Description

The vulnerability allows a remote attacker to bypass implemented security restrictions.

The vulnerability exists due to a race condition in the firewall process (dfwd). A remote attacker can bypass the firewall rule sets applied to the input loopback filter on any interfaces of a device.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Juniper Junos OS: 14.1 - 19.3

External links

http://kb.juniper.net/InfoCenter/index?page=content&id=JSA11140&cat=SIRT_1&actp=LIST

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.