How severe is CVE-2018-0421?

CVE-2018-0421 has a CVSS 3.x base score of 8.6, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2018-0421 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (88th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-0421?

CVE-2018-0421 primarily affects Cisco Prime Access Registrar. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2018-0421?

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-2018-0421 published?

CVE-2018-0421 was published on 2018-10-05 and last updated on 2026-06-17.

CVE-2018-0421

CVE-2018-0421 is a high-severity vulnerability in Cisco Prime Access Registrar with a CVSS 3.x base score of 8.6. 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-772.

Key facts

Severity: High (CVSS 3.x base score 8.6)
CVSS v2: 5.0
EPSS exploit prediction: 3% (88th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-772
Affected product: Cisco Prime Access Registrar
Published: 2018-10-05
Last modified: 2026-06-17

Description

A vulnerability in TCP connection management in Cisco Prime Access Registrar could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition when the application unexpectedly restarts. The vulnerability is due to incorrect handling of incoming TCP SYN packets to specific listening ports. The improper handling of the TCP SYN packets could cause a system file description to be allocated and not freed. An attacker could exploit this vulnerability by sending a crafted stream of TCP SYN packets to the application. A successful exploit could allow the attacker to cause the application to eventually restart if a file description cannot be obtained.

Frequently asked questions

What is CVE-2018-0421?: A vulnerability in TCP connection management in Cisco Prime Access Registrar could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition when the application unexpectedly restarts. The vulnerability is due to incorrect handling of incoming TCP SYN packets to specific listening ports. The improper handling of the TCP SYN packets could cause a system file description to be allocated and not freed. An attacker could exploit this vulnerability by sending a crafted stream of TCP SYN packets to the application. A successful exploit could allow the attacker to cause the application to eventually restart if a file description cannot be obtained.
How severe is CVE-2018-0421?: CVE-2018-0421 has a CVSS 3.x base score of 8.6, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2018-0421 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (88th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-0421?: CVE-2018-0421 primarily affects Cisco Prime Access Registrar. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2018-0421?: 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-2018-0421 published?: CVE-2018-0421 was published on 2018-10-05 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:cisco:prime_access_registrar:*:*:*:*:*:*:*:*
cpe:2.3:a:cisco:prime_access_registrar_jumpstart:*:*:*:*:*:*:*:*

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