Junos OS and Junos OS Evolved: Optional transitive BGP attribute is modified before propagation to peers causing sessions to flap

Summary

An Improper Check for Unusual or Exceptional Conditions vulnerability in the routing protocol daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated, network-based attacker to cause an availability impact for downstream devices. When an affected device receives a specific optional, transitive BGP attribute over an existing BGP session, it will be erroneously modified before propagation to peers. When the attribute is detected as malformed by the peers, these peers will most likely terminate the BGP sessions with the affected devices and thereby cause an availability impact due to the resulting routing churn. This issue affects: Junos OS: • all versions before 22.4R3-S8, • 23.2 versions before 23.2R2-S5 • 23.4 versions before 23.4R2-S6, • 24.2 versions before 24.2R2-S2, • 24.4 versions before 24.4R2; Junos OS Evolved:  • all versions before 22.4R3-S8-EVO, • 23.2 versions before 23.2R2-S5-EVO, • 23.4 versions before 23.4R2-S6-EVO, • 24.2 versions before 24.2R2-S2-EVO, • 24.4 versions before 24.4R2-EVO.

Timeline

1. Jan 15, 2026, 8:16 PM UTCCVE published
2. Jan 15, 2026, 9:10 PM UTCCISA SSVC assessment

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

3. Jan 15, 2026, 9:10 PM UTCRecord last updated

Affected versions

• Juniper Networks Junos OS

  fixed in 22.4R3-S8; From 23.2 · fixed in 23.2R2-S5; From 23.4 · fixed in 23.4R2-S6; From 24.2 · fixed in 24.2R2-S2; From 24.4 · fixed in 24.4R2

• Juniper Networks Junos OS Evolved

  fixed in 22.4R3-S8-EVO; From 23.2 · fixed in 23.2R2-S5-EVO; From 23.4 · fixed in 23.4R2-S6-EVO; From 24.2 · fixed in 24.2R2-S2-EVO; From 24.4 · fixed in 24.4R2-EVO

References 2