How severe is CVE-2021-1403?

CVE-2021-1403 has a CVSS 3.x base score of 7.4, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-1403 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-1403?

CVE-2021-1403 primarily affects Cisco Ios Xe. In total, 123 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-1403?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-1403 published?

CVE-2021-1403 was published on 2021-03-24 and last updated on 2026-06-17.

CVE-2021-1403

CVE-2021-1403 is a high-severity vulnerability in Cisco Ios Xe with a CVSS 3.x base score of 7.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1021.

Key facts

Severity: High (CVSS 3.x base score 7.4)
CVSS v2: 7.1
EPSS exploit prediction: 1% (44th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-1021
Affected product: Cisco Ios Xe
Published: 2021-03-24
Last modified: 2026-06-17

Description

A vulnerability in the web UI feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to conduct a cross-site WebSocket hijacking (CSWSH) attack and cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient HTTP protections in the web UI on an affected device. An attacker could exploit this vulnerability by persuading an authenticated user of the web UI to follow a crafted link. A successful exploit could allow the attacker to corrupt memory on the affected device, forcing it to reload and causing a DoS condition.

Frequently asked questions

What is CVE-2021-1403?: A vulnerability in the web UI feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to conduct a cross-site WebSocket hijacking (CSWSH) attack and cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient HTTP protections in the web UI on an affected device. An attacker could exploit this vulnerability by persuading an authenticated user of the web UI to follow a crafted link. A successful exploit could allow the attacker to corrupt memory on the affected device, forcing it to reload and causing a DoS condition.
How severe is CVE-2021-1403?: CVE-2021-1403 has a CVSS 3.x base score of 7.4, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-1403 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-1403?: CVE-2021-1403 primarily affects Cisco Ios Xe. In total, 123 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-1403?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-1403 published?: CVE-2021-1403 was published on 2021-03-24 and last updated on 2026-06-17.

References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-cswsh-FKk9AzT5

Affected products (123)

cpe:2.3:o:cisco:ios_xe:3.15.1xbs:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:3.15.2xbs:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.3.1:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.3.1a:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.3.2:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.3.3:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.3.4:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.3.5:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.3.5b:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.3.6:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.3.7:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.3.8:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.3.9:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.3.10:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.3.11:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.4.1:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.4.2:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.4.3:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.5.1:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.5.1a:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.5.1b:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.5.2:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.5.3:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.6.1:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.6.2:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.6.3:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.6.4:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.6.4a:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.6.4s:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.6.5:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.6.5a:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.6.5b:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.6.6:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.6.7:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.6.7a:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.6.8:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.7.1:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.7.1a:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.7.1b:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios_xe:16.7.2:*:*:*:*:*:*:*

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