Vulnerability Database

393,392

Total vulnerabilities in the database

CVE-2005-1021 — cisco / ios

Resource Management Errors

Memory leak in Secure Shell (SSH) in Cisco IOS 12.0 through 12.3, when authenticating against a TACACS+ server, allows remote attackers to cause a denial of service (memory consumption) via an incorrect username or password.

  • Published: May 2, 2005
  • Updated: Oct 3, 2026
  • CVE: CVE-2005-1021
  • Severity: High
  • Exploit:
  • CISA KEV:

CVSS v2:

  • Severity: High
  • Score: 7.1
  • AV:N/AC:M/Au:N/C:N/I:N/A:C

CWEs:

Software Affected versions
cisco / ios = 12.0s
cisco / ios = 12.0sx
cisco / ios = 12.1ax
cisco / ios = 12.1az
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 = 12.1eu
cisco / ios = 12.1ew
cisco / ios = 12.1ex
cisco / ios = 12.1t
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 = 12.1xl
cisco / ios = 12.1xm
cisco / ios = 12.1xp
cisco / ios = 12.1xq
cisco / ios = 12.1xr
cisco / ios = 12.1xt
cisco / ios = 12.1xu
cisco / ios = 12.1xv
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 = 12.2
cisco / ios = 12.2b
cisco / ios = 12.2dd
cisco / ios = 12.2dx
cisco / ios = 12.2eu
cisco / ios = 12.2ew
cisco / ios = 12.2ewa
cisco / ios = 12.2ex
cisco / ios = 12.2s
cisco / ios = 12.2se
cisco / ios = 12.2sea
cisco / ios = 12.2seb
cisco / ios = 12.2su
cisco / ios = 12.2sv
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 = 12.2xa
cisco / ios = 12.2xc
cisco / ios = 12.2xf
cisco / ios = 12.2xn
cisco / ios = 12.2xs
cisco / ios = 12.2ye
cisco / ios = 12.2yk
cisco / ios = 12.2yo
cisco / ios = 12.2yx
cisco / ios = 12.2yz
cisco / ios = 12.2za
cisco / ios = 12.3t
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 = 12.3xq
cisco / ios = 12.3xr
cisco / ios = 12.3xs
cisco / ios = 12.3xu
cisco / ios = 12.3xw
cisco / ios = 12.3xx
cisco / ios = 12.3xy
cisco / ios = 12.3ya
cisco / ios = 12.3yd
cisco / ios = 12.3yf
cisco / ios = 12.3yg
cisco / ios = 12.3yh
cisco / ios = 12.3yj
cisco / ios = 12.3yk

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.