CVE-2026-73442: Arista EOS VRRP Information Disclosure

CVE-2026-73442 Overview

CVE-2026-73442 affects Arista Networks EOS platforms running the Virtual Router Redundancy Protocol (VRRP). The vulnerability causes peer device VRRP authentication credentials to be written in cleartext to agent trace logs on the switch. An authenticated user with sufficient privileges to read those logs, or any system that receives forwarded log output, can recover the peer VRRP credentials. The attacker does not need direct access to the network segment where VRRP is running. This weakness is categorized under [CWE-532]: Insertion of Sensitive Information into Log File.

Critical Impact
Peer VRRP authentication credentials are exposed in cleartext logs, enabling credential recovery by anyone with log access without requiring presence on the VRRP network segment.

Affected Products

Arista EOS with VRRP enabled
Systems configured to forward EOS agent trace logs to external collectors
Refer to Arista Security Advisory #0157 for specific affected release trains

Discovery Timeline

2026-09-16 - CVE-2026-73442 published to NVD
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-73442

Vulnerability Analysis

VRRP allows multiple routers to share a virtual IP address for first-hop redundancy. When authentication is configured, VRRP peers exchange a shared secret in advertisement messages to prevent unauthorized routers from joining the group. Arista EOS parses these advertisements and writes diagnostic information into agent trace logs. The parsed advertisement content includes the peer authentication credential in cleartext form. Any operator with EOS privileges to read agent trace logs can retrieve the credential. If the switch forwards logs to a syslog collector or Security Information and Event Management (SIEM) system, the credential also reaches every downstream log consumer.

Root Cause

The root cause is improper handling of sensitive fields during trace logging. VRRP authentication data should be redacted or omitted before being written to persistent or forwardable log streams. Instead, the credential is serialized alongside other advertisement metadata. This matches [CWE-532], where sensitive information is inserted into a log file that is accessible to actors outside the intended trust boundary.

Attack Vector

The attack requires an authenticated user with sufficient privileges on the affected switch, or read access to a system that ingests forwarded EOS logs. Once the attacker retrieves the peer credential, they can impersonate a legitimate VRRP router if they later gain access to the VRRP segment. This can enable traffic redirection, man-in-the-middle positioning, or denial of service against first-hop routing. The vulnerability itself is an information disclosure issue and does not directly grant network-layer access.

No public proof-of-concept code is required. Reproduction consists of enabling VRRP with authentication, generating peer advertisements, and inspecting the agent trace logs on the affected EOS device.

Detection Methods for CVE-2026-73442

Indicators of Compromise

Presence of VRRP authentication strings inside EOS agent trace log files on affected switches
Forwarded syslog or SIEM records containing VRRP advertisement fields with plaintext credential values
Unexpected reads or exports of EOS trace log directories by operator accounts

Detection Strategies

Search log stores for VRRP advertisement fields adjacent to credential-shaped strings and alert on matches
Audit account activity for privileged users accessing agent trace logs on EOS devices
Correlate access to log collectors with subsequent VRRP configuration changes or unexpected master transitions

Monitoring Recommendations

Restrict and monitor access to any SIEM or log aggregation tier that ingests EOS trace output
Alert on VRRP state changes, priority modifications, and new master elections that do not map to planned changes
Track privileged EOS command usage such as show logging and bash sessions targeting trace directories

How to Mitigate CVE-2026-73442

Immediate Actions Required

Review Arista Security Advisory #0157 and identify EOS devices running a vulnerable release with VRRP enabled
Rotate VRRP authentication credentials on all affected groups after remediation, since existing secrets should be treated as exposed
Purge historical agent trace logs and forwarded log records that may contain the cleartext credentials
Restrict read access to EOS trace logs and downstream log collectors to a minimal set of administrators

Patch Information

Arista has published remediation guidance in Arista Security Advisory #0157. Apply the fixed EOS release identified in that advisory for your hardware platform and train. After upgrade, confirm that VRRP advertisement traces no longer contain plaintext credential fields.

Workarounds

Disable VRRP authentication where the deployment permits, since the exposed field is only populated when authentication is configured
Stop forwarding EOS agent trace logs to shared collectors until patched releases are installed
Tighten role-based access control (RBAC) so that only a limited set of accounts can read agent trace directories

bash

# Configuration example: restrict log forwarding and rotate VRRP secret after patching
# 1. Remove trace log forwarding target until patched
configure
no logging host <collector-ip>

# 2. After upgrading to the fixed EOS release, rotate the VRRP authentication key
interface Vlan100
  vrrp 1 authentication text <new-strong-secret>
end
write memory