An Improper Input Validation vulnerability in the Routing Protocol Daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated, network-based attacker to cause a Denial of Service (DoS).
 

When a BGP update message is received over an established BGP session, and that message contains a specific, optional transitive attribute, this session will be torn down with an update message error. This issue cannot propagate beyond an affected system as the processing error occurs as soon as the update is received. This issue is exploitable remotely as the respective attribute can propagate through unaffected systems and intermediate AS (if any).

Continuous receipt of a BGP update containing this attribute will create a sustained Denial of Service (DoS) condition.

Some customers have experienced these BGP session flaps which prompted Juniper SIRT to release this advisory out of cycle before fixed releases are widely available as there is an effective workaround.

This issue affects:

Juniper Networks Junos OS:

• 15.1R1 and later versions prior to 20.4R3-S8;
• 21.1 version 21.1R1 and later versions prior to 21.2R3-S6;
• 21.3 versions prior to 21.3R3-S5;
• 21.4 versions prior to 21.4R3-S4;
• 22.1 versions prior to 22.1R3-S4;
• 22.2 versions prior to 22.2R3-S2;
• 22.3 versions prior to 22.3R2-S2, 22.3R3-S1;
• 22.4 versions prior to 22.4R2-S1, 22.4R3;
• 23.1 versions prior to 23.1R1-S1, 23.1R2.

Juniper Networks Junos OS Evolved:

• All versions prior to 20.4R3-S8-EVO;
• 21.1 version 21.1R1-EVO and later versions prior to 21.2R3-S6-EVO;
• 21.3 versions prior to 21.3R3-S5-EVO;
• 21.4 versions prior to 21.4R3-S4-EVO;
• 22.1 versions prior to 22.1R3-S4-EVO;
• 22.2 versions prior to 22.2R3-S2-EVO;
• 22.3 versions prior to 22.3R2-S2-EVO, 22.3R3-S1-EVO;
• 22.4 versions prior to 22.4R2-S1-EVO, 22.4R3-EVO;
• 23.1 versions prior to 23.1R1-S1-EVO, 23.1R2-EVO.

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-2023-0026.
 

The following software releases have been updated to resolve this specific issue:

Junos OS: 20.4R3-S8*, 21.2R3-S6*, 21.3R3-S5*, 21.4R3-S4, 22.1R3-S4*, 22.2R3-S2*, 22.3R2-S2*, 22.3R3-S1*, 22.4R2-S1*, 22.4R3*, 23.1R1-S1*, 23.1R2*, 23.2R1*, and all subsequent releases;

Junos OS Evolved: 20.4R3-S8-EVO*, 21.2R3-S6-EVO*, 21.3R3-S5-EVO*, 21.4R3-S4-EVO, 22.1R3-S4-EVO*, 22.2R3-S2-EVO*, 22.3R2-S2-EVO*, 22.3R3-S1-EVO*, 22.4R2-S1-EVO*, 22.4R3-EVO*, 23.1R1-S1-EVO*, 23.1R2-EVO*, 23.2R1-EVO*, and all subsequent releases.

*Pending Publication

This issue is being tracked as 1739919

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

The workaround is to configure BGP error tolerance by way of:
 

which causes malformed BGP routes to be 'treated as withdrawal' instead of bringing down the BGP session.

Additional details can be found at https://www.juniper.net/documentation/us/en/software/junos/bgp/topics/topic-map/bgp-error-messages.html

Juniper considers configuring this option to be a Best Common Practice (BCP) as it not only prevents this issue from happening, but protects against similar issues as well.

2023-06-21: 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-2023-0026 at cve.mitre.org
• https://kb.juniper.net/JSA71542/ [juniper.net]
• https://www.juniper.net/documentation/us/en/software/junos/bgp/topics/topic-map/bgp-error-messages.html