Vulnerability Database

393,392

Total vulnerabilities in the database

CVE-2005-1020 — cisco / ios

Improper Authentication

Secure Shell (SSH) 2 in Cisco IOS 12.0 through 12.3 allows remote attackers to cause a denial of service (device reload) (1) via a username that contains a domain name when using a TACACS+ server to authenticate, (2) when a new SSH session is in the login phase and a currently logged in user issues a send command, or (3) when IOS is logging messages and an SSH session is terminated while the server is sending data.

  • Published: May 2, 2005
  • Updated: Oct 3, 2026
  • CVE: CVE-2005-1020
  • Severity: High
  • Exploit:
  • CISA KEV:

CVSS v2:

  • Severity: High
  • Score: 7.1
  • AV:N/AC:M/Au:N/C:N/I:N/A:C
Software Affected versions
cisco / ios = 12.0
cisco / ios = 12.0(23)s4
cisco / ios = 12.0(23)s5
cisco / ios = 12.0(24)s1
cisco / ios = 12.0(24)s4
cisco / ios = 12.0(24)s5
cisco / ios = 12.0(24.2)s
cisco / ios = 12.0(26)s1
cisco / ios = 12.0(27)s
cisco / ios = 12.0(27)sv
cisco / ios = 12.0(27)sv1
cisco / ios = 12.0da
cisco / ios = 12.0db
cisco / ios = 12.0dc
cisco / ios = 12.0s
cisco / ios = 12.0sc
cisco / ios = 12.0sl
cisco / ios = 12.0sp
cisco / ios = 12.0st
cisco / ios = 12.0sv
cisco / ios = 12.0sx
cisco / ios = 12.0sy
cisco / ios = 12.0sz
cisco / ios = 12.0t
cisco / ios = 12.0w5
cisco / ios = 12.0wc
cisco / ios = 12.0wt
cisco / ios = 12.0wx
cisco / ios = 12.0xa
cisco / ios = 12.0xb
cisco / ios = 12.0xc
cisco / ios = 12.0xd
cisco / ios = 12.0xe
cisco / ios = 12.0xf
cisco / ios = 12.0xg
cisco / ios = 12.0xh
cisco / ios = 12.0xi
cisco / ios = 12.0xj
cisco / ios = 12.0xk
cisco / ios = 12.0xl
cisco / ios = 12.0xm
cisco / ios = 12.0xn
cisco / ios = 12.0xp
cisco / ios = 12.0xq
cisco / ios = 12.0xr
cisco / ios = 12.0xs
cisco / ios = 12.0xt
cisco / ios = 12.0xu
cisco / ios = 12.0xv
cisco / ios = 12.0xw
cisco / ios = 12.1
cisco / ios = 12.1(11)e
cisco / ios = 12.1(11b)e
cisco / ios = 12.1(11b)e12
cisco / ios = 12.1(11b)e14
cisco / ios = 12.1(13)e9
cisco / ios = 12.1(19)e1
cisco / ios = 12.1(20)e
cisco / ios = 12.1(20)e1
cisco / ios = 12.1(20)e2
cisco / ios = 12.1(20)ea1
cisco / ios = 12.1(20)ec
cisco / ios = 12.1(20)ec1
cisco / ios = 12.1(20)eo
cisco / ios = 12.1(20)ew
cisco / ios = 12.1(20)ew1
cisco / ios = 12.1aa
cisco / ios = 12.1ax
cisco / ios = 12.1ay
cisco / ios = 12.1az
cisco / ios = 12.1cx
cisco / ios = 12.1da
cisco / ios = 12.1db
cisco / ios = 12.1dc
cisco / ios = 12.1e
cisco / ios = 12.1ea
cisco / ios = 12.1eb
cisco / ios = 12.1ec
cisco / ios = 12.1eo
cisco / ios = 12.1eu
cisco / ios = 12.1ev
cisco / ios = 12.1ew
cisco / ios = 12.1ex
cisco / ios = 12.1ey
cisco / ios = 12.1m
cisco / ios = 12.1t
cisco / ios = 12.1xa
cisco / ios = 12.1xb
cisco / ios = 12.1xc
cisco / ios = 12.1xd
cisco / ios = 12.1xe
cisco / ios = 12.1xf
cisco / ios = 12.1xg
cisco / ios = 12.1xh
cisco / ios = 12.1xi
cisco / ios = 12.1xj
cisco / ios = 12.1xk
cisco / ios = 12.1xl
cisco / ios = 12.1xm
cisco / ios = 12.1xp
cisco / ios = 12.1xq
cisco / ios = 12.1xr
cisco / ios = 12.1xs
cisco / ios = 12.1xt
cisco / ios = 12.1xu
cisco / ios = 12.1xv
cisco / ios = 12.1xw
cisco / ios = 12.1xx
cisco / ios = 12.1xy
cisco / ios = 12.1xz
cisco / ios = 12.1ya
cisco / ios = 12.1yb
cisco / ios = 12.1yc
cisco / ios = 12.1yd
cisco / ios = 12.1ye
cisco / ios = 12.1yf
cisco / ios = 12.1yh
cisco / ios = 12.1yi
cisco / ios = 12.1yj
cisco / ios = 12.2
cisco / ios = 12.2(1)xa
cisco / ios = 12.2(1)xd
cisco / ios = 12.2(1)xd1
cisco / ios = 12.2(1)xd3
cisco / ios = 12.2(1)xd4
cisco / ios = 12.2(1)xe
cisco / ios = 12.2(1)xe2
cisco / ios = 12.2(1)xe3
cisco / ios = 12.2(1)xh
cisco / ios = 12.2(1)xq
cisco / ios = 12.2(1)xs
cisco / ios = 12.2(1)xs1
cisco / ios = 12.2(2)t4
cisco / ios = 12.2(2)xa
cisco / ios = 12.2(2)xa1
cisco / ios = 12.2(2)xa5
cisco / ios = 12.2(2)xb
cisco / ios = 12.2(2)xb3
cisco / ios = 12.2(2)xb4
cisco / ios = 12.2(2)xf
cisco / ios = 12.2(2)xg
cisco / ios = 12.2(2)xh
cisco / ios = 12.2(2)xh2
cisco / ios = 12.2(2)xh3
cisco / ios = 12.2(2)xi
cisco / ios = 12.2(2)xi1
cisco / ios = 12.2(2)xi2
cisco / ios = 12.2(2)xj
cisco / ios = 12.2(2)xj1
cisco / ios = 12.2(2)xk
cisco / ios = 12.2(2)xk2
cisco / ios = 12.2(2)xn
cisco / ios = 12.2(2)xt
cisco / ios = 12.2(2)xt3
cisco / ios = 12.2(2)xu
cisco / ios = 12.2(2)xu2
cisco / ios = 12.2(4)ja
cisco / ios = 12.2(4)ja1
cisco / ios = 12.2(8)ja
cisco / ios = 12.2(11)ja
cisco / ios = 12.2(11)ja1
cisco / ios = 12.2(11)t
cisco / ios = 12.2(12g)
cisco / ios = 12.2(12h)
cisco / ios = 12.2(14)sy
cisco / ios = 12.2(14)sy1
cisco / ios = 12.2(14)sz
cisco / ios = 12.2(14)za
cisco / ios = 12.2(14)za2
cisco / ios = 12.2(14.5)
cisco / ios = 12.2(14.5)t
cisco / ios = 12.2(15)zn
cisco / ios = 12.2(15.1)s
cisco / ios = 12.2(16)b
cisco / ios = 12.2(16.1)b
cisco / ios = 12.2(17a)sxa
cisco / ios = 12.2(18)ew
cisco / ios = 12.2(18)ewa
cisco / ios = 12.2(18)s
cisco / ios = 12.2(18)se
cisco / ios = 12.2(18)sv
cisco / ios = 12.2(18)sw
cisco / ios = 12.2(20)ew
cisco / ios = 12.2(20)s
cisco / ios = 12.2(20)s1
cisco / ios = 12.2(21)
cisco / ios = 12.2(21a)
cisco / ios = 12.2(23)
cisco / ios = 12.2b
cisco / ios = 12.2bc
cisco / ios = 12.2bw
cisco / ios = 12.2bx
cisco / ios = 12.2by
cisco / ios = 12.2bz
cisco / ios = 12.2cx
cisco / ios = 12.2cy
cisco / ios = 12.2cz
cisco / ios = 12.2da
cisco / ios = 12.2dd
cisco / ios = 12.2dx
cisco / ios = 12.2ew
cisco / ios = 12.2ewa
cisco / ios = 12.2ja
cisco / ios = 12.2jk
cisco / ios = 12.2mb
cisco / ios = 12.2mc
cisco / ios = 12.2mx
cisco / ios = 12.2s
cisco / ios = 12.2se
cisco / ios = 12.2su
cisco / ios = 12.2sv
cisco / ios = 12.2sw
cisco / ios = 12.2sx
cisco / ios = 12.2sxa
cisco / ios = 12.2sxb
cisco / ios = 12.2sxd
cisco / ios = 12.2sy
cisco / ios = 12.2sz
cisco / ios = 12.2t
cisco / ios = 12.2x
cisco / ios = 12.2xa
cisco / ios = 12.2xb
cisco / ios = 12.2xc
cisco / ios = 12.2xd
cisco / ios = 12.2xe
cisco / ios = 12.2xf
cisco / ios = 12.2xg
cisco / ios = 12.2xh
cisco / ios = 12.2xi
cisco / ios = 12.2xj
cisco / ios = 12.2xk
cisco / ios = 12.2xl
cisco / ios = 12.2xm
cisco / ios = 12.2xn
cisco / ios = 12.2xq
cisco / ios = 12.2xr
cisco / ios = 12.2xs
cisco / ios = 12.2xt
cisco / ios = 12.2xu
cisco / ios = 12.2xw
cisco / ios = 12.2xz
cisco / ios = 12.2ya
cisco / ios = 12.2yb
cisco / ios = 12.2yc
cisco / ios = 12.2yd
cisco / ios = 12.2ye
cisco / ios = 12.2yf
cisco / ios = 12.2yg
cisco / ios = 12.2yh
cisco / ios = 12.2yj
cisco / ios = 12.2yk
cisco / ios = 12.2yl
cisco / ios = 12.2ym
cisco / ios = 12.2yn
cisco / ios = 12.2yo
cisco / ios = 12.2yp
cisco / ios = 12.2yq
cisco / ios = 12.2yr
cisco / ios = 12.2ys
cisco / ios = 12.2yt
cisco / ios = 12.2yu
cisco / ios = 12.2yv
cisco / ios = 12.2yw
cisco / ios = 12.2yx
cisco / ios = 12.2yy
cisco / ios = 12.2yz
cisco / ios = 12.2za
cisco / ios = 12.2zb
cisco / ios = 12.2zc
cisco / ios = 12.2zd
cisco / ios = 12.2ze
cisco / ios = 12.2zf
cisco / ios = 12.2zg
cisco / ios = 12.2zh
cisco / ios = 12.2zi
cisco / ios = 12.2zj
cisco / ios = 12.2zk
cisco / ios = 12.2zl
cisco / ios = 12.2zm
cisco / ios = 12.2zn
cisco / ios = 12.2zo
cisco / ios = 12.2zp
cisco / ios = 12.2zq
cisco / ios = 12.3
cisco / ios = 12.3(2)t3
cisco / ios = 12.3(2)xc1
cisco / ios = 12.3(2)xc2
cisco / ios = 12.3(4)t
cisco / ios = 12.3(4)t1
cisco / ios = 12.3(4)t2
cisco / ios = 12.3(4)t3
cisco / ios = 12.3(4)xd
cisco / ios = 12.3(4)xd1
cisco / ios = 12.3(5)
cisco / ios = 12.3(5a)
cisco / ios = 12.3(5a)b
cisco / ios = 12.3(5b)
cisco / ios = 12.3(6)
cisco / ios = 12.3b
cisco / ios = 12.3bc
cisco / ios = 12.3bw
cisco / ios = 12.3j
cisco / ios = 12.3ja
cisco / ios = 12.3t
cisco / ios = 12.3xa
cisco / ios = 12.3xb
cisco / ios = 12.3xc
cisco / ios = 12.3xd
cisco / ios = 12.3xe
cisco / ios = 12.3xf
cisco / ios = 12.3xg
cisco / ios = 12.3xh
cisco / ios = 12.3xi
cisco / ios = 12.3xj
cisco / ios = 12.3xk
cisco / ios = 12.3xl
cisco / ios = 12.3xm
cisco / ios = 12.3xn
cisco / ios = 12.3xq
cisco / ios = 12.3xr
cisco / ios = 12.3xs
cisco / ios = 12.3xt
cisco / ios = 12.3xu
cisco / ios = 12.3xv
cisco / ios = 12.3xw
cisco / ios = 12.3xx
cisco / ios = 12.3xy
cisco / ios = 12.3xz
cisco / ios = 12.3ya
cisco / ios = 12.3yc
cisco / ios = 12.3yd
cisco / ios = 12.3ye
cisco / ios = 12.3yf
cisco / ios = 12.3yg
cisco / ios = 12.3yh
cisco / ios = 12.3yj
cisco / ios = 12.3yl

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.