Arista EOS: Replay protection not applied in IPsec AutoVPN with dynamic paths
Summary
Arista EOS devices running IPsec AutoVPN with dynamic paths may not apply the configured IPsec replay window as expected. As a result, anti-replay protection can be silently inactive even when it is configured in an SA policy. The issue does not allow decryption of IPsec traffic, but an attacker with network access may be able to replay previously valid protected traffic.
Affected
- Arista EOS 4.27.0F to below 4.28.0F
- Arista EOS 4.28.0F to 4.28.13M
- Arista EOS 4.29.0F to below 4.30.0F
- Arista EOS 4.30.0F to below 4.31.0F
- Arista EOS 4.31.0F to below 4.32.0F
- Arista EOS 4.32.0F to below 4.33.0F
- Arista EOS 4.33.0F to 4.33.8M
- Arista EOS 4.34.0F to 4.34.7M
- Arista EOS 4.35.0F to 4.35.5M
- Arista EOS 4.36.0F to 4.36.1F (end point disputed between sources; the Arista advisory is authoritative)
- Only with IPsec AutoVPN configured with dynamic paths. Default configuration is unaffected.
- Affected platforms include AWE 5000 Series, AWE 7200R Series and CloudEOS.
Fixed in
Unknown. Check the Arista advisory for the fixed builds.
Workaround
Unknown. No vendor-documented workaround was found.
Exploitation
- No reports of exploitation in the wild found.
- No public proof of concept found.
- CISA KEV and GitHub advisories were not checked directly.
Our recommendation
- Check whether AutoVPN with dynamic paths is used on Arista EOS devices.
- Compare the running EOS version with the Arista advisory 25041 and plan an upgrade to a fixed build.
- Review the anti-replay configuration of the SA policy until the fix is applied.
- Recheck NVD and CISA KEV for changes.
- Relevance is likely low for most SMEs, as these are enterprise WAN and cloud routers.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Arista Security Advisory 0219 www.arista.com
- CVE Record CVE-2026-120974 www.cve.org
- Strix CVE-2026-120974 www.strix.ai
- ThreatInt CVE-2026-120974 cve.threatint.com
- Arista AutoVPN Dynamic Path Selection www.arista.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 11 Nov 2026, 09:58.
Original description (NVD)
On affected platforms running Arista EOS with IPsec AutoVPN Feature configured with dynamic paths, the configured IPsec replay window may not be applied as expected. As a result, IPsec anti-replay protection may be silently inactive even when it has been configured via an SA policy, contrary to the operator's expectation. This issue does not allow decryption of the affected IPsec traffic, but it may allow replay of previously valid protected traffic.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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