# CVE-2026-121288: Security Advisory 0221

Status: published. Published: 2026-11-10. Updated: 2026-11-13.

An unauthenticated attacker on an adjacent network segment can bypass MD5 authentication and have unauthorized RIP route updates accepted by the device. Successful exploitation requires that RIPv2 MD5 authentication is configured on the affected interface. An attacker who can inject crafted RIPv2 packets could cause the device to install routes that redirect network traffic through attacker-controlled paths, create routing loops, or blackhole traffic, disrupting network connectivity.

## Remediation

- workaround: switch(config)# router rip
switch(config-router-rip)# shutdown
switch(config-router-rip)# end

Note: disabling RIP or changing network statements may withdraw routes and interrupt connectivity. Plan a change window, confirm alternate routing, and verify the resulting configuration and route behavior. (source: CNA: Arista)

## Affected products and versions

- Arista Networks / EOS: 4.37.0F (affected, custom); ≥ 4.36.0F; ≤ 4.36.2F (affected, custom); ≥ 4.35.0F; ≤ 4.35.6M (affected, custom); ≥ 4.34.0F; ≤ 4.34.8M (affected, custom); ≥ 4.33.0F; ≤ 4.33.10M (affected, custom); ≥ 4.32.0F; < 4.33.0F (affected, custom); ≥ 1.0.0; < 4.32.0F (affected, custom). Source: CNA: Arista; platforms: 710 Series, 720D Series, 720XP/722XPM Series, 750X Series, 7010TX Series, 7020R/R4 Series, 7130 Series running EOS, 7170 Series, 7050X3/X4 Series, 7060X/X2/X4/X5/X6/XE7 Series, 7260X/X3 Series, 7280R/R2/R3/R4 Series, 7300X/X3 Series, 7320X Series, 7358X4 Series, 7368X4 Series, 7388X5 Series, 7500R/R2/R3 Series, 7800R3/R4 Series, 7700R4 Series, AWE 5000 Series, AWE 7200R Series, CloudEOS, cEOS-lab, vEOS-lab, CloudVision eXchange, virtual or physical appliance

## Severity and prioritization

- CVSS 3.1: 8.1 (high); CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H; source: CNA: Arista

- CVSS 4.0: 6.1 (medium); CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:L/SA:L; source: CNA: Arista

- CVSS 4.0: 6.1 (medium); CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: psirt@arista.com

- CVSS 3.1: 8.1 (high); CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H; source: NVD: psirt@arista.com

- CISA KEV: No listing in collected sources

- EPSS: 0.24% as of 2026-11-13; percentile 14.79%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-303

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://www.arista.com/en/support/advisories-notices/security-advisory/25043-security-advisory-0221 (CNA: Arista; vendor-advisory)

- https://www.arista.com/en/support/advisories-notices/security-advisory/25043-security-advisory-0221 (psirt@arista.com)

## Provenance

- CNA: Arista: https://www.cve.org/CVERecord?id=CVE-2026-121288; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-121288; retrieved 2026-11-13; source updated 2026-11-12

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-121288; retrieved 2026-11-13; source updated Not reported

Revision: 8392e5af0ebf38bc846b6c8061c5190fd671e27b82164cc7d952fc888745d19d

Canonical: https://y2.dev/cve/CVE-2026-121288

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