CVE-2021-1590

Cisco NX-OS Software system login block-for Denial of Service Vulnerability

MEDIUM

5.3

CVSS Score

Published: August 25, 2021 at 07:11 PM UTC

Updated: June 17, 2026 at 03:32 AM UTC

103 products affected across 1 vendorNx OSUnified Computing SystemNexus 9508

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Severity

MEDIUM5.3

Exploit prediction

EPSS 1%

SSVC

No known exploit

Description

A vulnerability in the implementation of the system login block-for command for Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a login process to unexpectedly restart, causing a denial of service (DoS) condition. This vulnerability is due to a logic error in the implementation of the system login block-for command when an attack is detected and acted upon. An attacker could exploit this vulnerability by performing a brute-force login attack on an affected device. A successful exploit could allow the attacker to cause a login process to reload, which could result in a delay during authentication to the affected device.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Nx OS · Cisconpm

95%

7.0(3)i4(0.116)7.3(7)n1(1b)

cisco-nexus-3000 (environment) · cisco-nexus-3048 (environment) · cisco-nexus-31108pc-v (environment) · cisco-nexus-31108tc-v (environment) · cisco-nexus-31128pq (environment) · cisco-nexus-3132c-z (environment) · cisco-nexus-3132q-v (environment) · cisco-nexus-3132q-x-3132q-xl (environment) · cisco-nexus-3164q (environment) · cisco-nexus-3172pq-pq-xl (environment) · cisco-nexus-3172tq-xl (environment) · cisco-nexus-3232c (environment) · cisco-nexus-3264c-e (environment) · cisco-nexus-3264q (environment) · cisco-nexus-3408-s (environment) · cisco-nexus-34180yc (environment) · cisco-nexus-3432d-s (environment) · cisco-nexus-3464c (environment) · cisco-nexus-3524-x-xl (environment) · cisco-nexus-3548-x-xl (environment) · cisco-nexus-36180yc-r (environment) · cisco-nexus-3636c-r (environment) · cisco-nexus-5548p (environment) · cisco-nexus-5548up (environment) · cisco-nexus-5596t (environment) · cisco-nexus-5596up (environment) · cisco-nexus-56128p (environment) · cisco-nexus-5624q (environment) · cisco-nexus-5648q (environment) · cisco-nexus-5672up (environment) · cisco-nexus-5672up-16g (environment) · cisco-nexus-5696q (environment) · cisco-nexus-6001 (environment) · cisco-nexus-6004 (environment) · cisco-nexus-7000-10-slot (environment) · cisco-nexus-7000-18-slot (environment) · cisco-nexus-7000-4-slot (environment) · cisco-nexus-7000-9-slot (environment) · cisco-nexus-7000-supervisor-1 (environment) · cisco-nexus-7000-supervisor-2 (environment) · cisco-nexus-7000-supervisor-2e (environment) · cisco-nexus-7004 (environment) · cisco-nexus-7009 (environment) · cisco-nexus-7010 (environment) · cisco-nexus-7018 (environment) · cisco-nexus-7700 (environment) · cisco-nexus-7700-10-slot (environment) · cisco-nexus-7700-18-slot (environment) · cisco-nexus-7700-2-slot (environment) · cisco-nexus-7700-6-slot (environment) · cisco-nexus-7700-supervisor-2e (environment) · cisco-nexus-7700-supervisor-3e (environment) · cisco-nexus-7702 (environment) · cisco-nexus-7706 (environment) · cisco-nexus-7710 (environment) · cisco-nexus-7718 (environment) · cisco-nexus-9000v (environment) · cisco-nexus-92160yc-x (environment) · cisco-nexus-92300yc (environment) · cisco-nexus-92304qc (environment) · cisco-nexus-92348gc-x (environment) · cisco-nexus-9236c (environment) · cisco-nexus-9272q (environment) · cisco-nexus-93108tc-ex (environment) · cisco-nexus-93108tc-ex-24 (environment) · cisco-nexus-93108tc-fx (environment) · cisco-nexus-93108tc-fx-24 (environment) · cisco-nexus-93108tc-fx3p (environment) · cisco-nexus-93120tx (environment) · cisco-nexus-93128tx (environment) · cisco-nexus-9316d-gx (environment) · cisco-nexus-93180lc-ex (environment) · cisco-nexus-93180yc-ex (environment) · cisco-nexus-93180yc-ex-24 (environment) · cisco-nexus-93180yc-fx (environment) · cisco-nexus-93180yc-fx-24 (environment) · cisco-nexus-93180yc-fx3 (environment) · cisco-nexus-93180yc-fx3s (environment) · cisco-nexus-93216tc-fx2 (environment) · cisco-nexus-93240yc-fx2 (environment) · cisco-nexus-9332c (environment) · cisco-nexus-9332pq (environment) · cisco-nexus-93360yc-fx2 (environment) · cisco-nexus-9336c-fx2 (environment) · cisco-nexus-9336c-fx2-e (environment) · cisco-nexus-9348gc-fxp (environment) · cisco-nexus-93600cd-gx (environment) · cisco-nexus-9364c (environment) · cisco-nexus-9364c-gx (environment) · cisco-nexus-9372px (environment) · cisco-nexus-9372px-e (environment) · cisco-nexus-9372tx (environment) · cisco-nexus-9372tx-e (environment) · cisco-nexus-9396px (environment) · cisco-nexus-9396tx (environment) · cisco-nexus-9508 (environment)

Unified Computing System · Cisco

95%

v < 4.0(4m)4.1 ≤ v < 4.1(3d)

Affected range stops below 4.0(4m), so it looks safe — our inference, not a vendor statement

Affected range stops below 4.1(3d), so it looks safe — our inference, not a vendor statement

cisco-unified-computing-system-6248up (same device) · cisco-unified-computing-system-6296up (same device) · cisco-unified-computing-system-6324 (same device) · cisco-unified-computing-system-6332 (same device) · cisco-unified-computing-system-6332-16up (same device)

Nexus 3000 · Ciscodevice

80%

All versions

Nexus 3048 · Ciscodevice

80%

All versions

Nexus 31108Pc-V · Ciscodevice

80%

All versions

Nexus 31108Tc-V · Ciscodevice

80%

All versions