How severe is CVE-2019-12656?

CVE-2019-12656 has a CVSS 3.x base score of 7.5, 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-2019-12656 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-12656?

CVE-2019-12656 primarily affects Cisco Ios. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-12656?

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-2019-12656 published?

CVE-2019-12656 was published on 2019-09-25 and last updated on 2026-06-17.

CVE-2019-12656

CVE-2019-12656 is a high-severity vulnerability in Cisco Ios with a CVSS 3.x base score of 7.5. 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-20.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Cisco Ios
Published: 2019-09-25
Last modified: 2026-06-17

Description

A vulnerability in the IOx application environment of multiple Cisco platforms could allow an unauthenticated, remote attacker to cause the IOx web server to stop processing HTTPS requests, resulting in a denial of service (DoS) condition. The vulnerability is due to a Transport Layer Security (TLS) implementation issue. An attacker could exploit this vulnerability by sending crafted TLS packets to the IOx web server on an affected device. A successful exploit could allow the attacker to cause the IOx web server to stop processing HTTPS requests, resulting in a DoS condition.

Frequently asked questions

What is CVE-2019-12656?: A vulnerability in the IOx application environment of multiple Cisco platforms could allow an unauthenticated, remote attacker to cause the IOx web server to stop processing HTTPS requests, resulting in a denial of service (DoS) condition. The vulnerability is due to a Transport Layer Security (TLS) implementation issue. An attacker could exploit this vulnerability by sending crafted TLS packets to the IOx web server on an affected device. A successful exploit could allow the attacker to cause the IOx web server to stop processing HTTPS requests, resulting in a DoS condition.
How severe is CVE-2019-12656?: CVE-2019-12656 has a CVSS 3.x base score of 7.5, 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-2019-12656 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-12656?: CVE-2019-12656 primarily affects Cisco Ios. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-12656?: 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-2019-12656 published?: CVE-2019-12656 was published on 2019-09-25 and last updated on 2026-06-17.

References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190925-iox

Affected products (7)

cpe:2.3:o:cisco:ios:1.6.0.0:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ios:1.8.0:*:*:*:*:*:*:*
cpe:2.3:o:cisco:industrial_ethernet_2000_series_firmware:15.2\(6\)e:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ic3000_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ie_4000_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:cisco:cgr_1000_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:cisco:ir510_wpan_firmware:-:*:*:*:*:*:*:*

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