Vulnerability Database

346,508

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: Nov 9, 2025
  • CVE: CVE-2019-1738
  • Severity: High
  • Exploit:

CVSS v3:

  • Severity: High
  • Score: 7.5
  • AV:N/AC:L/PR:N/UI:N/S:U/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 From Fixed in
cisco / ios 15.6(1)t2 15.6(1)t2.x
cisco / ios 15.3(3)jpc 15.3(3)jpc.x
cisco / ios 15.5(3)s1a 15.5(3)s1a.x
cisco / ios 15.5(3)m4a 15.5(3)m4a.x
cisco / ios_xe 16.2.1 16.2.1.x
cisco / ios_xe 3.18.2s 3.18.2s.x
cisco / ios 15.6(2)t1 15.6(2)t1.x
cisco / ios_xe 3.17.3s 3.17.3s.x
cisco / ios_xe 3.16.0s 3.16.0s.x
cisco / ios 15.6(3)m1 15.6(3)m1.x
cisco / ios_xe 3.16.4s 3.16.4s.x
cisco / ios 15.5(3)sn 15.5(3)sn.x
cisco / ios 15.3(3)jnp 15.3(3)jnp.x
cisco / ios_xe 3.17.1as 3.17.1as.x
cisco / ios 15.6(1)s2 15.6(1)s2.x
cisco / ios 15.5(3)s5 15.5(3)s5.x
cisco / ios_xe 3.18.2asp 3.18.2asp.x
cisco / ios_xe 3.18.3s 3.18.3s.x
cisco / ios 15.5(3)m3 15.5(3)m3.x
cisco / ios_xe 3.18.0as 3.18.0as.x
cisco / ios 15.5(3)m2 15.5(3)m2.x
cisco / ios_xe 3.16.2s 3.16.2s.x
cisco / ios 15.3(3)jd2 15.3(3)jd2.x
cisco / ios_xe 3.16.0cs 3.16.0cs.x
cisco / ios 15.6(2)s 15.6(2)s.x
cisco / ios 15.6(2)s2 15.6(2)s2.x
cisco / ios 15.5(3)s4 15.5(3)s4.x
cisco / ios 15.3(3)ja1n 15.3(3)ja1n.x
cisco / ios 15.3(3)jpb 15.3(3)jpb.x
cisco / ios 15.5(3)m 15.5(3)m.x
cisco / ios_xe 3.18.1sp 3.18.1sp.x
cisco / ios 15.3(3)jpc1 15.3(3)jpc1.x
cisco / ios_xe 3.17.4s 3.17.4s.x
cisco / ios 15.6(1)s4 15.6(1)s4.x
cisco / ios 15.6(2)t2 15.6(2)t2.x
cisco / ios 15.6(2)sn 15.6(2)sn.x
cisco / ios 15.3(3)jpb1 15.3(3)jpb1.x
cisco / ios 15.5(3)m1 15.5(3)m1.x
cisco / ios_xe 3.16.5s 3.16.5s.x
cisco / ios 15.5(3)s2 15.5(3)s2.x
cisco / ios_xe 3.16.1s 3.16.1s.x
cisco / ios 15.6(2)s4 15.6(2)s4.x
cisco / ios_xe 3.2.0ja 3.2.0ja.x
cisco / ios 15.5(3)s1 15.5(3)s1.x
cisco / ios 15.3(3)jnp1 15.3(3)jnp1.x
cisco / ios 15.5(3)m0a 15.5(3)m0a.x
cisco / ios 15.5(3)s 15.5(3)s.x
cisco / ios 15.6(1)t1 15.6(1)t1.x
cisco / ios 15.6(3)m1b 15.6(3)m1b.x
cisco / ios_xe 3.18.1bsp 3.18.1bsp.x
cisco / ios_xe 3.18.1csp 3.18.1csp.x
cisco / ios_xe 3.18.0s 3.18.0s.x
cisco / ios 15.6(3)m 15.6(3)m.x
cisco / ios 15.6(1)s3 15.6(1)s3.x
cisco / ios_xe 3.17.0s 3.17.0s.x
cisco / ios_xe 3.16.4ds 3.16.4ds.x
cisco / ios 15.6(1)s1 15.6(1)s1.x
cisco / ios 15.6(2)t 15.6(2)t.x
cisco / ios 15.6(3)m0a 15.6(3)m0a.x
cisco / ios 15.6(2)s3 15.6(2)s3.x
cisco / ios 15.3(3)jd 15.3(3)jd.x
cisco / ios 15.6(1)t0a 15.6(1)t0a.x
cisco / ios_xe 3.16.3s 3.16.3s.x
cisco / ios 15.3(3)jnp3 15.3(3)jnp3.x
cisco / ios_xe 3.17.1s 3.17.1s.x
cisco / ios_xe 3.18.2sp 3.18.2sp.x
cisco / ios 15.6(1)s 15.6(1)s.x
cisco / ios_xe 16.4.1 16.4.1.x
cisco / ios_xe 3.16.2bs 3.16.2bs.x
cisco / ios_xe 3.16.1as 3.16.1as.x
cisco / ios_xe 3.18.1s 3.18.1s.x
cisco / ios_xe 16.2.2 16.2.2.x
cisco / ios 15.6(2)s1 15.6(2)s1.x
cisco / ios_xe 3.18.0sp 3.18.0sp.x
cisco / ios 15.5(3)m4 15.5(3)m4.x
cisco / ios_xe 3.16.3as 3.16.3as.x
cisco / ios_xe 3.16.4as 3.16.4as.x
cisco / ios 15.5(3)m5 15.5(3)m5.x
cisco / ios 15.3(3)jpc2 15.3(3)jpc2.x
cisco / ios_xe 3.16.4bs 3.16.4bs.x
cisco / ios 15.5(3)s0a 15.5(3)s0a.x
cisco / ios 15.5(3)s3 15.5(3)s3.x
cisco / ios_xe 16.3.1 16.3.1.x
cisco / ios_xe 3.16.2as 3.16.2as.x
cisco / ios_xe 3.18.1asp 3.18.1asp.x
cisco / ios 15.6(1)t 15.6(1)t.x
cisco / ios_xe 16.3.1a 16.3.1a.x
cisco / ios_xe 16.3.2 16.3.2.x
cisco / ios_xe 16.3.3 16.3.3.x
cisco / ios 15.3(3)jd3 15.3(3)jd3.x
cisco / ios 15.3(3)jpc3 15.3(3)jpc3.x
cisco / ios 15.3(3)jd4 15.3(3)jd4.x
cisco / ios 15.3(3)jpd 15.3(3)jpd.x
cisco / ios_xe 16.5.1 16.5.1.x
cisco / ios 15.3(3)je 15.3(3)je.x
cisco / ios 15.3(3)jd7 15.3(3)jd7.x
cisco / ios 15.3(3)jf1 15.3(3)jf1.x
cisco / ios_xe 16.5.1a 16.5.1a.x
cisco / ios_xe 16.3.4 16.3.4.x
cisco / ios_xe 16.5.1b 16.5.1b.x
cisco / ios_xe 16.4.2 16.4.2.x
cisco / ios 15.5(3)m4b 15.5(3)m4b.x
cisco / ios 15.5(3)m4c 15.5(3)m4c.x
cisco / ios 15.5(3)m5a 15.5(3)m5a.x
cisco / ios 15.6(3)m1a 15.6(3)m1a.x
cisco / ios 15.6(1)sn2 15.6(1)sn2.x
cisco / ios 15.1(3)svo2 15.1(3)svo2.x
cisco / ios_xe 3.16.4gs 3.16.4gs.x
cisco / ios_xe 3.16.4cs 3.16.4cs.x
cisco / ios 15.6(1)sn1 15.6(1)sn1.x
cisco / ios 15.6(1)sn3 15.6(1)sn3.x
cisco / ios_xe 3.16.4es 3.16.4es.x
cisco / ios 15.6(6)sn 15.6(6)sn.x
cisco / ios 15.1(3)svk4c 15.1(3)svk4c.x
cisco / ios 15.5(3)sn0a 15.5(3)sn0a.x
cisco / ios 15.6(1)sn 15.6(1)sn.x
cisco / ios_xe 3.16.5as 3.16.5as.x
cisco / ios 15.6(5)sn 15.6(5)sn.x
cisco / ios 15.6(7)sn 15.6(7)sn.x
cisco / ios 15.1(3)svp1 15.1(3)svp1.x
cisco / ios 15.6(2)sp3b 15.6(2)sp3b.x
cisco / ios 15.2(3)ea1 15.2(3)ea1.x
cisco / ios_xe 3.16.0bs 3.16.0bs.x
cisco / ios 15.6(4)sn 15.6(4)sn.x
cisco / ios 15.2(4a)ea5 15.2(4a)ea5.x
cisco / ios 15.6(3)sn 15.6(3)sn.x
cisco / ios 15.1(3)svk4b 15.1(3)svk4b.x
cisco / ios 15.1(2)sg8a 15.1(2)sg8a.x
cisco / ios 15.1(4)m12c 15.1(4)m12c.x
cisco / ios_xe 16.4.3 16.4.3.x
cisco / ios 15.6(2)t0a 15.6(2)t0a.x
cisco / ios 15.3(3)ji 15.3(3)ji.x
cisco / ios 15.1(3)svg3d 15.1(3)svg3d.x
cisco / ios_xe 3.18.1isp 3.18.1isp.x
cisco / ios 15.1(3)svn2 15.1(3)svn2.x
cisco / ios 15.1(3)svi1b 15.1(3)svi1b.x
cisco / ios_xe 3.18.1gsp 3.18.1gsp.x
cisco / ios 15.3(3)jf35 15.3(3)jf35.x
cisco / ios_xe 3.18.4s 3.18.4s.x
cisco / ios 15.1(3)svo1 15.1(3)svo1.x
cisco / ios 15.1(3)svm3 15.1(3)svm3.x
cisco / ios 15.3(3)ji2 15.3(3)ji2.x
cisco / ios_xe 3.18.1hsp 3.18.1hsp.x
cisco / ios 15.5(3)m2a 15.5(3)m2a.x
cisco / ios_xe 3.16.0as 3.16.0as.x
cisco / ios 15.3(3)jd9 15.3(3)jd9.x
cisco / ios 15.3(3)jd11 15.3(3)jd11.x
cisco / ios 15.3(3)jh 15.3(3)jh.x
cisco / ios 15.3(3)jd12 15.3(3)jd12.x
cisco / ios 15.3(3)jd13 15.3(3)jd13.x
cisco / ios 15.3(3)jd6 15.3(3)jd6.x
cisco / ios 15.3(3)jd8 15.3(3)jd8.x
cisco / ios 15.3(3)jd5 15.3(3)jd5.x
cisco / ios 15.3(3)jg1 15.3(3)jg1.x
cisco / ios 15.3(3)jd14 15.3(3)jd14.x
cisco / ios 15.3(3)jf5 15.3(3)jf5.x
cisco / ios 15.3(3)jg 15.3(3)jg.x
cisco / ios 15.3(3)jf 15.3(3)jf.x
cisco / ios 15.3(3)jf4 15.3(3)jf4.x
cisco / ios 15.3(3)jf2 15.3(3)jf2.x
cisco / ios 15.1(3)svo3 15.1(3)svo3.x
cisco / ios 15.1(3)svo4 15.1(3)svo4.x
cisco / ios 15.1(3)svp2 15.1(3)svp2.x
cisco / ios 15.3(3)jpc5 15.3(3)jpc5.x

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.