EUVD-2026-79238
GHSA-78f4-9r4h-vc9q
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:H/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
Unauthenticated crafted packet (PR:N/AC:L) drops a BFD session; scope changes as routing protocols on other systems react (S:C, A:H), minor integrity to routing state (I:L), no confidentiality.
Primary rating from Vendor (arista).
CVSS VectorVendor: arista
Lifecycle Timeline
2DescriptionCVE.org
On affected platforms running Arista EOS with authenticated Bidirectional Forwarding Detection (BFD) sessions configured, a specially crafted packet can cause the BFD session(s) to go down. This may result in undesirable network changes because various routing protocols monitor status on BFD session(s).
AnalysisAI
Crafted Bidirectional Forwarding Detection (BFD) control packets can force authenticated BFD sessions on Arista EOS to drop, which in turn triggers reconvergence in the routing protocols that monitor those sessions (BGP, OSPF, IS-IS, or static-route failover) and can disrupt or blackhole traffic. The root cause is CWE-303, an incorrect implementation of the authentication algorithm: a packet that should fail BFD authentication is mishandled and can terminate the session, and the published CVSS 4.0 vector scores this 9.2 with unauthenticated network access (PR:N, UI:N) and high subsequent-system availability impact. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires the target Arista EOS device to have authenticated Bidirectional Forwarding Detection (BFD) sessions explicitly configured - this is the specific feature that must be enabled and is the primary limiting factor. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is a genuine availability threat but a narrower one than its 9.2 CVSS 4.0 score suggests in isolation. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Vendor patch availability is not specified in the supplied intelligence, so confirm fixed EOS maintenance releases directly against the Arista advisory at https://www.arista.com/en/support/advisories-notices/security-advisory/24710-security-advisory-0154 and upgrade to the earliest patched build in your 4.33/4.34/4.35/4.36 train (or a later train) rather than assuming that the current release is fixed. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory the Arista EOS estate and flag every device running 4.33.0 through 4.33.8M, 4.34.0 through 4.34.7M, 4.35.0 through 4.35.5M, or 4.36.0 through 4.36.1F, then confirm which of those have authenticated BFD sessions explicitly configured on BGP, OSPF, IS-IS, or static-route failover; open a case with Arista TAC referencing CVE-2026-73458 to request a hotfix or target fixed release, and begin capturing routing-protocol and BFD logs so any session flaps can be correlated to malicious traffic. …
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