VulnerabilityPublished 10 Nov 2026

CVE-2026-121294: Arista Networks EOS · Improper Validation of Specified Quantity in Input

Affects Arista Networks EOSSource CVE Database V5

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Not known to be exploited · CVSS 5.3 Medium · fixed in 4.33.0F : update Arista Networks EOS when convenient.

Data as of 10 Nov 2026, 20:32 UTC

CVSS 3.1 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (Arista)	CVSS 3.1	5.3
CNA (Arista)	CVSS 4.0	6.9

Patch: Available – fixed in 4.33.0F, 4.32.0F, 4.29.0F

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 10 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Arista Networks EOS to 4.33.0F, 4.32.0F or 4.29.0F.

Affected software

Product	Affected	Fixed in
Arista NetworksEOS	Affected >=4.36.0F <=4.36.2F >=4.35.0F <=4.35.6M >=4.34.0F <=4.34.8M >=4.33.0F <=4.33.10M >=4.32.0F <4.33.0F >=4.29.0F <4.32.0F >=4.28.2F <4.29.0F	Fixed in 4.33.0F 4.32.0F 4.29.0F

AI-suggested

Fixed versions are available starting from 4.29.0F, 4.32.0F, and 4.33.0F. Users should upgrade affected EOS versions to these or later releases to remediate the vulnerability. Since this is not a cloud service, manual patching is required. No other mitigation or workaround is indicated.

Description

CVE-2026-121294 is a medium-severity vulnerability in Arista Networks EOS affecting versions from 4.28.2F up to 4.36.2F. It involves improper validation of specified quantity in input related to the S-BFD reflector proxy. An unauthenticated attacker can send a crafted S-BFD Protocol Data Unit (PDU) that may cause the device to temporarily stop reflecting S-BFD packets, potentially leading to S-BFD session timeouts.

Impact

The vulnerability can cause a temporary denial of service condition by stopping the reflection of S-BFD packets, which may lead to session timeouts. There is no impact on confidentiality or integrity. The attack requires no privileges or user interaction and can be performed remotely over the network.

Summary

This vulnerability (CWE-1284) affects Arista EOS platforms configured with an S-BFD reflector proxy. The flaw allows an unauthenticated attacker to send a specially crafted S-BFD PDU that might cause the device to temporarily cease reflecting S-BFD packets. This disruption can result in S-BFD session timeouts, impacting the availability of the S-BFD service. The issue is present in multiple EOS versions ranging from 4.28.2F through 4.36.2F. Fixed versions include 4.29.0F, 4.32.0F, and 4.33.0F, indicating that patches are available in these releases.

CWE-1284Improper Validation of Specified Quantity in Input (opens in a new tab)
Base weakness
The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

arista.com/en/support/advisories-notices/security-advisory/25045-security-advisory-0223 (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 10 Nov 2026, 20:32 UTC

WeaknessesCWE-1284

Technical details

References

Community reviews

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