CVE-2026-73438

Security Advisory 0172

Published Sep 16, 2026 CVSS 4.0 · 7 High EPSS < 1% KEV · Not listed
Description
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.

Remediation

Vendor Solution

The recommended resolution is to upgrade to a remediated software version at your earliest convenience. Arista recommends customers move to the latest version of each release that contains all the fixes listed below. CVE-2026-73438 has been fixed in the following releases: - 4.36.2F and later releases in the 4.36.x train - 4.35.6M and later releases in the 4.35.x train - 4.34.8M and later releases in the 4.34.x train - 4.33.10M and later releases in the 4.33.x train No hotfix is available for this issue.


Vendor Workaround

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.

Tracking

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Advisories

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History
Type Values Removed Values Added
First Time appeared Arista
Arista eos
Vendors & Products Arista
Arista eos
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description 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.
Title Security Advisory 0172
Weaknesses CWE-617
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 7, 'vector': 'CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
Arista
Published
Updated
Sep 16, 2026, 6:03 PM
Reserved
Aug 12, 2026, 4:39 PM
Status
Awaiting Analysis
Published
Sep 16, 2026, 10:16 AM
Modified
Sep 16, 2026, 7:17 PM