CVE-2026-73438

Summary

On affected platforms running Arista EOS with Open Shortest Path First version 3 (OSPFv3) configured, an unauthenticated attacker on the same OSPFv3 broadcast domain can send a specially crafted set of packets that can cause the Ospf3 agent to restart unexpectedly. The crash results in the loss of all OSPFv3 adjacencies on the affected device and may disrupt routing across the broader OSPF domain until the agent recovers.

This issue was reported externally by Dravanet Inc., and Arista is not aware of any malicious exploitation of this vulnerability in customer networks.

Affected Software

VendorProductVersion RangeStatus
Arista NetworksEOS4.36.0F <= 4.36.1Faffected
Arista NetworksEOS4.35.0F <= 4.35.5Maffected
Arista NetworksEOS4.34.0F <= 4.34.7Maffected
Arista NetworksEOS4.33.0F <= 4.33.9Maffected
Arista NetworksEOS1.0.0 < 4.33.0Faffected

Weaknesses

  • CWE-617: CWE-617 Reachable Assertion

Workarounds

The OSPFv3 authentication feature helps to mitigate this vulnerability. OSPFv3 authentication prevents unauthorized actors from injecting crafted packets into the OSPF domain. Enabling it on all OSPFv3-speaking interfaces ensures that packets from unauthenticated senders are discarded before they can trigger this vulnerability.

Per-interface OSPFv3 encryption:

Configure ESP-based encryption with authentication on each OSPFv3 interface. All peers on the same interface must use the same SPI, algorithm, and passphrase.

switch(config)# interface <interface-name> switch(config-if)# ospfv3 encryption ipsec spi <spi-value> esp aes-256-cbc sha1 passphrase <shared-passphrase>

Per-area OSPFv3 configuration:

Configure ESP-based encryption with authentication on each OSPFv3 area.

switch(config)# router ospfv3 switch(config-router-ospfv3)# address-family ipv4 switch(config-router-ospfv3-af)# area <area-id> encryption ipsec spi <spi-value> esp aes-256-cbc sha1 passphrase <shared-passphrase> switch(config-router-ospfv3-af)# address-family ipv6 switch(config-router-ospfv3-af)# area <area-id> encryption ipsec spi <spi-value> esp aes-256-cbc sha1 passphrase <shared-passphrase>

Caution: Enabling OSPFv3 authentication must be coordinated across peering neighbors simultaneously. Applying this configuration to a single peer will temporarily break the routing adjacency, resulting in traffic disruption.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References