Vulnerability Database

346,508

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: Nov 9, 2025
  • CVE: CVE-2005-1021
  • Severity: High
  • Exploit:

CVSS v2:

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

CWEs:

Software From Fixed in
cisco / ios 12.1xg 12.1xg.x
cisco / ios 12.3xr 12.3xr.x
cisco / ios 12.1xm 12.1xm.x
cisco / ios 12.1xi 12.1xi.x
cisco / ios 12.1e 12.1e.x
cisco / ios 12.3ya 12.3ya.x
cisco / ios 12.1xp 12.1xp.x
cisco / ios 12.1ya 12.1ya.x
cisco / ios 12.1yd 12.1yd.x
cisco / ios 12.3xs 12.3xs.x
cisco / ios 12.2sx 12.2sx.x
cisco / ios 12.3xg 12.3xg.x
cisco / ios 12.3xd 12.3xd.x
cisco / ios 12.3xm 12.3xm.x
cisco / ios 12.3xw 12.3xw.x
cisco / ios 12.2su 12.2su.x
cisco / ios 12.2ew 12.2ew.x
cisco / ios 12.2b 12.2b.x
cisco / ios 12.2sea 12.2sea.x
cisco / ios 12.1t 12.1t.x
cisco / ios 12.3xi 12.3xi.x
cisco / ios 12.1xr 12.1xr.x
cisco / ios 12.1az 12.1az.x
cisco / ios 12.2sxa 12.2sxa.x
cisco / ios 12.1db 12.1db.x
cisco / ios 12.3yj 12.3yj.x
cisco / ios 12.1xe 12.1xe.x
cisco / ios 12.3xj 12.3xj.x
cisco / ios 12.3t 12.3t.x
cisco / ios 12.2dd 12.2dd.x
cisco / ios 12.1eu 12.1eu.x
cisco / ios 12.1yf 12.1yf.x
cisco / ios 12.1xl 12.1xl.x
cisco / ios 12.1ax 12.1ax.x
cisco / ios 12.2sxb 12.2sxb.x
cisco / ios 12.2yo 12.2yo.x
cisco / ios 12.2t 12.2t.x
cisco / ios 12.2sv 12.2sv.x
cisco / ios 12.2seb 12.2seb.x
cisco / ios 12.2za 12.2za.x
cisco / ios 12.2xn 12.2xn.x
cisco / ios 12.2ye 12.2ye.x
cisco / ios 12.1yb 12.1yb.x
cisco / ios 12.3yd 12.3yd.x
cisco / ios 12.1eb 12.1eb.x
cisco / ios 12.2ex 12.2ex.x
cisco / ios 12.1dc 12.1dc.x
cisco / ios 12.1ex 12.1ex.x
cisco / ios 12.1yi 12.1yi.x
cisco / ios 12.3xf 12.3xf.x
cisco / ios 12.3xl 12.3xl.x
cisco / ios 12.2se 12.2se.x
cisco / ios 12.1yh 12.1yh.x
cisco / ios 12.3yk 12.3yk.x
cisco / ios 12.3yf 12.3yf.x
cisco / ios 12.1ec 12.1ec.x
cisco / ios 12.2sy 12.2sy.x
cisco / ios 12.1xh 12.1xh.x
cisco / ios 12.1xu 12.1xu.x
cisco / ios 12.3yg 12.3yg.x
cisco / ios 12.3xu 12.3xu.x
cisco / ios 12.3xy 12.3xy.x
cisco / ios 12.2xc 12.2xc.x
cisco / ios 12.2ewa 12.2ewa.x
cisco / ios 12.3xe 12.3xe.x
cisco / ios 12.2xs 12.2xs.x
cisco / ios 12.2sz 12.2sz.x
cisco / ios 12.1xd 12.1xd.x
cisco / ios 12.2dx 12.2dx.x
cisco / ios 12.3xq 12.3xq.x
cisco / ios 12.3xh 12.3xh.x
cisco / ios 12.1xq 12.1xq.x
cisco / ios 12.0s 12.0s.x
cisco / ios 12.2xf 12.2xf.x
cisco / ios 12.1ea 12.1ea.x
cisco / ios 12.2eu 12.2eu.x
cisco / ios 12.1xf 12.1xf.x
cisco / ios 12.3yh 12.3yh.x
cisco / ios 12.1ew 12.1ew.x
cisco / ios 12.2 12.2.x
cisco / ios 12.3xx 12.3xx.x
cisco / ios 12.1yc 12.1yc.x
cisco / ios 12.2yk 12.2yk.x
cisco / ios 12.2sxd 12.2sxd.x
cisco / ios 12.2yz 12.2yz.x
cisco / ios 12.2xa 12.2xa.x
cisco / ios 12.1xt 12.1xt.x
cisco / ios 12.0sx 12.0sx.x
cisco / ios 12.1ye 12.1ye.x
cisco / ios 12.3xk 12.3xk.x
cisco / ios 12.1xv 12.1xv.x
cisco / ios 12.2yx 12.2yx.x
cisco / ios 12.2s 12.2s.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.