CVE-2021-1279 | Cisco SD-WAN Denial of Service Vulnerabilities

Multiple vulnerabilities in Cisco SD-WAN products could allow an unauthenticated, remote attacker to execute denial of service (DoS) attacks against an affected device. For more information about these vulnerabilities, see the Details section of this advisory.

Published: 2021-01-20 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-1279 is rated Moderate Risk (59.2/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.39%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-1279

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.60% 1.39% +0.79%
2 2025-03-30 0.80% 0.60% -0.21%
3 2025-03-29 — 0.80% —

Full EPSS history (12 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-1279

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.6 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 4.0 [email protected]
8.6 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 4.0 [email protected]
7.8 2.0 HIGH
AV:N/AC:L/Au:N/C:N/I:N/A:C Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:C)
Complete availability impact.
 10.0 6.9 [email protected]

Weakness enumeration for CVE-2021-1279

Affected software / configurations for CVE-2021-1279

Vendor Product Version Raw CPE
cisco ios_xe_sd-wan — cpe:2.3:o:cisco:ios_xe_sd-wan:-:*:*:*:*:*:*:*
cisco sd-wan_firmware 18.3.5 cpe:2.3:o:cisco:sd-wan_firmware:18.3.5:*:*:*:*:*:*:*
cisco sd-wan_firmware 18.3.8 cpe:2.3:o:cisco:sd-wan_firmware:18.3.8:*:*:*:*:*:*:*
cisco sd-wan_firmware 18.4.1 cpe:2.3:o:cisco:sd-wan_firmware:18.4.1:*:*:*:*:*:*:*
cisco sd-wan_firmware 18.4.4 cpe:2.3:o:cisco:sd-wan_firmware:18.4.4:*:*:*:*:*:*:*
cisco sd-wan_firmware 18.4.5 cpe:2.3:o:cisco:sd-wan_firmware:18.4.5:*:*:*:*:*:*:*
cisco sd-wan_firmware 19.2.0 cpe:2.3:o:cisco:sd-wan_firmware:19.2.0:*:*:*:*:*:*:*
cisco sd-wan_firmware 19.2.1 cpe:2.3:o:cisco:sd-wan_firmware:19.2.1:*:*:*:*:*:*:*
cisco sd-wan_firmware 19.2.2 cpe:2.3:o:cisco:sd-wan_firmware:19.2.2:*:*:*:*:*:*:*
cisco sd-wan_firmware 19.2.99 cpe:2.3:o:cisco:sd-wan_firmware:19.2.99:*:*:*:*:*:*:*
cisco sd-wan_firmware 20.1.0 cpe:2.3:o:cisco:sd-wan_firmware:20.1.0:*:*:*:*:*:*:*
cisco sd-wan_vsmart_controller_firmware — cpe:2.3:o:cisco:sd-wan_vsmart_controller_firmware:*:*:*:*:*:*:*:*
cisco catalyst_sd-wan_manager — cpe:2.3:a:cisco:catalyst_sd-wan_manager:-:*:*:*:*:*:*:*
cisco sd-wan_vbond_orchestrator — cpe:2.3:a:cisco:sd-wan_vbond_orchestrator:-:*:*:*:*:*:*:*

References for CVE-2021-1279

cvelogic Threat Intelligence