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iOSOperating system · Cisco

CVE-2009-2863

HIGH · 7.1 CVSS v2.0 Published 2009-09-28
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
80/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Race condition in the Firewall Authentication Proxy feature in Cisco IOS 12.0 through 12.4 allows remote attackers to bypass authentication, or bypass the consent web page, via a crafted request, aka Bug ID CSCsy15227.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A race condition in the Firewall Authentication Proxy feature in Cisco IOS versions 12.0 through 12.4 allows remote attackers to bypass authentication mechanisms or bypass the consent web page by sending crafted requests.

MitigationUpgrade Cisco IOS to a version beyond 12.4 that addresses this vulnerability; if immediate upgrade is not feasible, implement additional network-level access controls and monitor for unauthorized access attempts.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
iOSOperating system
Affected:= 12.0xk= 12.0xr= 12.1= 12.1e= 12.1ex= 12.1t= 12.1xc= 12.1xh= 12.1xi= 12.1xj= 12.1xm= 12.1xp

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
M
Authentication
None
Confidentiality
Complete
Integrity
None
Availability
None

AV:N/AC:M/Au:N/C:C/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the device operating system
    Run 'show version' or check the device prompt/boot sequence to confirm the device runs Cisco IOS (not IOS-XE, NX-OS, ASA, or other platforms)
    Affected if The device is not running Cisco IOS - this vulnerability only affects Cisco IOS
  2. Determine the Cisco IOS version
    Execute 'show version' and locate the version string (for example, 12.1(3)T or 12.0(5)S)
    Affected if The installed IOS version matches or falls within the 12.0xk, 12.0xr, 12.1, 12.1e, 12.1ex, 12.1t, 12.1xc, 12.1xh, 12.1xi, 12.1xj, 12.1xm, or 12.1xp trains listed as affected
  3. Check if Firewall Authentication Proxy is enabled
    Run 'show running-config | include authentication' or 'show ip auth-proxy' to inspect the configuration for authentication proxy settings
    Affected if Firewall Authentication Proxy (also called auth-proxy or IP Auth-proxy) is configured and active on any interface

The device is affected if it runs Cisco IOS versions 12.0xk, 12.0xr, 12.1 through 12.1xp and has the Firewall Authentication Proxy feature enabled.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Cisco IOS to a version beyond 12.4 that addresses this vulnerability; if immediate upgrade is not feasible, implement additional network-level access controls and monitor for unauthorized access attempts.

Fix this in iOS Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2009-2863 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data