Vulnerability Database

393,392

Total vulnerabilities in the database

CVE-2019-1738 — cisco / ios

Improper Input Validation

A vulnerability in the Network-Based Application Recognition (NBAR) feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload. This vulnerability is due to a parsing issue on DNS packets. An attacker could exploit these vulnerabilities by sending crafted DNS packets through routers that are running an affected version and have NBAR enabled. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition.

  • Published: Mar 28, 2019
  • Updated: Oct 3, 2026
  • CVE: CVE-2019-1738
  • Severity: High
  • Exploit:
  • CISA KEV:

CVSS v3:

  • Severity: High
  • Score: 8.6
  • AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

CVSS v2:

  • Severity: High
  • Score: 7.8
  • AV:N/AC:L/Au:N/C:N/I:N/A:C

CWEs:

Software Affected versions
cisco / ios = 15.1(2)sg8a
cisco / ios = 15.1(3)svg3d
cisco / ios = 15.1(3)svi1b
cisco / ios = 15.1(3)svk4b
cisco / ios = 15.1(3)svk4c
cisco / ios = 15.1(3)svm3
cisco / ios = 15.1(3)svn2
cisco / ios = 15.1(3)svo1
cisco / ios = 15.1(3)svo2
cisco / ios = 15.1(3)svo3
cisco / ios = 15.1(3)svo4
cisco / ios = 15.1(3)svp1
cisco / ios = 15.1(3)svp2
cisco / ios = 15.1(4)m12c
cisco / ios = 15.2(3)ea1
cisco / ios = 15.2(4a)ea5
cisco / ios = 15.3(3)ja1n
cisco / ios = 15.3(3)jd
cisco / ios = 15.3(3)jd2
cisco / ios = 15.3(3)jd3
cisco / ios = 15.3(3)jd4
cisco / ios = 15.3(3)jd5
cisco / ios = 15.3(3)jd6
cisco / ios = 15.3(3)jd7
cisco / ios = 15.3(3)jd8
cisco / ios = 15.3(3)jd9
cisco / ios = 15.3(3)jd11
cisco / ios = 15.3(3)jd12
cisco / ios = 15.3(3)jd13
cisco / ios = 15.3(3)jd14
cisco / ios = 15.3(3)je
cisco / ios = 15.3(3)jf
cisco / ios = 15.3(3)jf1
cisco / ios = 15.3(3)jf2
cisco / ios = 15.3(3)jf4
cisco / ios = 15.3(3)jf5
cisco / ios = 15.3(3)jf35
cisco / ios = 15.3(3)jg
cisco / ios = 15.3(3)jg1
cisco / ios = 15.3(3)jh
cisco / ios = 15.3(3)ji
cisco / ios = 15.3(3)ji2
cisco / ios = 15.3(3)jnp
cisco / ios = 15.3(3)jnp1
cisco / ios = 15.3(3)jnp3
cisco / ios = 15.3(3)jpb
cisco / ios = 15.3(3)jpb1
cisco / ios = 15.3(3)jpc
cisco / ios = 15.3(3)jpc1
cisco / ios = 15.3(3)jpc2
cisco / ios = 15.3(3)jpc3
cisco / ios = 15.3(3)jpc5
cisco / ios = 15.3(3)jpd
cisco / ios = 15.5(3)m
cisco / ios = 15.5(3)m0a
cisco / ios = 15.5(3)m1
cisco / ios = 15.5(3)m2
cisco / ios = 15.5(3)m2a
cisco / ios = 15.5(3)m3
cisco / ios = 15.5(3)m4
cisco / ios = 15.5(3)m4a
cisco / ios = 15.5(3)m4b
cisco / ios = 15.5(3)m4c
cisco / ios = 15.5(3)m5
cisco / ios = 15.5(3)m5a
cisco / ios = 15.5(3)s
cisco / ios = 15.5(3)s0a
cisco / ios = 15.5(3)s1
cisco / ios = 15.5(3)s1a
cisco / ios = 15.5(3)s2
cisco / ios = 15.5(3)s3
cisco / ios = 15.5(3)s4
cisco / ios = 15.5(3)s5
cisco / ios = 15.5(3)sn
cisco / ios = 15.5(3)sn0a
cisco / ios = 15.6(1)s
cisco / ios = 15.6(1)s1
cisco / ios = 15.6(1)s2
cisco / ios = 15.6(1)s3
cisco / ios = 15.6(1)s4
cisco / ios = 15.6(1)sn
cisco / ios = 15.6(1)sn1
cisco / ios = 15.6(1)sn2
cisco / ios = 15.6(1)sn3
cisco / ios = 15.6(1)t
cisco / ios = 15.6(1)t0a
cisco / ios = 15.6(1)t1
cisco / ios = 15.6(1)t2
cisco / ios = 15.6(2)s
cisco / ios = 15.6(2)s1
cisco / ios = 15.6(2)s2
cisco / ios = 15.6(2)s3
cisco / ios = 15.6(2)s4
cisco / ios = 15.6(2)sn
cisco / ios = 15.6(2)sp3b
cisco / ios = 15.6(2)t
cisco / ios = 15.6(2)t0a
cisco / ios = 15.6(2)t1
cisco / ios = 15.6(2)t2
cisco / ios = 15.6(3)m
cisco / ios = 15.6(3)m0a
cisco / ios = 15.6(3)m1
cisco / ios = 15.6(3)m1a
cisco / ios = 15.6(3)m1b
cisco / ios = 15.6(3)sn
cisco / ios = 15.6(4)sn
cisco / ios = 15.6(5)sn
cisco / ios = 15.6(6)sn
cisco / ios = 15.6(7)sn
cisco / ios_xe = 3.2.0ja
cisco / ios_xe = 3.16.0as
cisco / ios_xe = 3.16.0bs
cisco / ios_xe = 3.16.0cs
cisco / ios_xe = 3.16.0s
cisco / ios_xe = 3.16.1as
cisco / ios_xe = 3.16.1s
cisco / ios_xe = 3.16.2as
cisco / ios_xe = 3.16.2bs
cisco / ios_xe = 3.16.2s
cisco / ios_xe = 3.16.3as
cisco / ios_xe = 3.16.3s
cisco / ios_xe = 3.16.4as
cisco / ios_xe = 3.16.4bs
cisco / ios_xe = 3.16.4cs
cisco / ios_xe = 3.16.4ds
cisco / ios_xe = 3.16.4es
cisco / ios_xe = 3.16.4gs
cisco / ios_xe = 3.16.4s
cisco / ios_xe = 3.16.5as
cisco / ios_xe = 3.16.5s
cisco / ios_xe = 3.17.0s
cisco / ios_xe = 3.17.1as
cisco / ios_xe = 3.17.1s
cisco / ios_xe = 3.17.3s
cisco / ios_xe = 3.17.4s
cisco / ios_xe = 3.18.0as
cisco / ios_xe = 3.18.0s
cisco / ios_xe = 3.18.0sp
cisco / ios_xe = 3.18.1asp
cisco / ios_xe = 3.18.1bsp
cisco / ios_xe = 3.18.1csp
cisco / ios_xe = 3.18.1gsp
cisco / ios_xe = 3.18.1hsp
cisco / ios_xe = 3.18.1isp
cisco / ios_xe = 3.18.1s
cisco / ios_xe = 3.18.1sp
cisco / ios_xe = 3.18.2asp
cisco / ios_xe = 3.18.2s
cisco / ios_xe = 3.18.2sp
cisco / ios_xe = 3.18.3s
cisco / ios_xe = 3.18.4s
cisco / ios_xe = 16.2.1
cisco / ios_xe = 16.2.2
cisco / ios_xe = 16.3.1
cisco / ios_xe = 16.3.1a
cisco / ios_xe = 16.3.2
cisco / ios_xe = 16.3.3
cisco / ios_xe = 16.3.4
cisco / ios_xe = 16.4.1
cisco / ios_xe = 16.4.2
cisco / ios_xe = 16.4.3
cisco / ios_xe = 16.5.1
cisco / ios_xe = 16.5.1a
cisco / ios_xe = 16.5.1b

Frequently Asked Questions

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.