2023-06: Out-of-Cycle Security Bulletin: Junos OS and Junos OS Evolved: A BGP session will flap upon receipt of a specific, optional transitive attribute

Description

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.

Timeline

Scores

EPSS (exploitation in 30 days)

0.65% · top 49% of all CVEs (8 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: yes · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.

Weakness

• CWE-20 Improper Input Validation (opens in a new tab)All about CWE-20 and its CVEs
• Denial of Service (DoS)

Affected products

• Juniper Networks · Junos OS

  • unaffected unspecified – < 15.1R1
  • affected unspecified – < 20.4R3-S8
  • affected 21.1 – < 21.1*
  • affected 21.2 – < 21.2R3-S6
  • affected 21.3 – < 21.3R3-S5
  • affected 21.4 – < 21.4R3-S4
  • affected 22.1 – < 22.1R3-S4
  • affected 22.2 – < 22.3R2-S2, 22.3R3-S1
  • affected 22.3 – < 22.2R3-S2
  • affected 22.4 – < 22.4R2-S1, 22.4R3
  • affected 23.1 – < 23.1R1-S1, 23.1R2

• Juniper Networks · Junos OS Evolved

  • affected unspecified – < 20.4R3-S8-EVO
  • affected 21.1R1-EVO – < 21.1*
  • affected 21.2 – < 21.2R3-S6-EVO
  • affected 21.3 – < 21.3R3-S5-EVO
  • affected 21.4 – < 21.4R3-S4-EVO
  • affected 22.1 – < 22.1R3-S4-EVO
  • affected 22.2 – < 22.2R3-S2-EVO
  • affected 22.3 – < 22.3R2-S2-EVO, 22.3R3-S1-EVO
  • affected 22.4 – < 22.4R2-S1-EVO, 22.4R3-EVO
  • affected 23.1 – < 23.1R1-S1-EVO, 23.1R2-EVO

What to do

Solution: 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

Workaround: The workaround is to configure BGP error tolerance by way of: [ protocols bgp bgp-error-tolerance ... ] 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.

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

References (2)

• https://supportportal.juniper.net/JSA71542 (opens in a new tab)vendor-advisoryx_transferred
• https://www.juniper.net/documentation/us/en/software/junos/bgp/topics/topic-map/bgp-error-messages.html (opens in a new tab)productx_transferred

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2023-0026](https://cveledger.app/badge/CVE-2023-0026.svg)](https://cveledger.app/cve/CVE-2023-0026)

Record last updated 6 Dec 2024, 19:18 UTC.