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iOSOperating system · Cisco

CVE-2011-3273

HIGH · 7.8 CVSS v2.0 Published 2011-10-03
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
87/100
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
Memory leak in Cisco IOS 15.0 through 15.1, when IPS or Zone-Based Firewall (aka ZBFW) is configured, allows remote attackers to cause a denial of service (memory consumption or device crash) via vectors that trigger many session creation flows, aka Bug ID CSCti79848.

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 · moderate confidence

Memory leak in Cisco IOS versions 15.0 through 15.1 when IPS (Intrusion Prevention System) or Zone-Based Firewall (ZBFW) is configured. Remote attackers can trigger the leak by generating many session creation flows, causing memory exhaustion and potentially device crash, resulting in denial of service.

MitigationUpdate Cisco IOS to a patched version beyond 15.1. If immediate update is not possible, consider rate-limiting session creation or temporarily disabling IPS/ZBFW features if not critical, while planning the upgrade.

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:= 15.0= 15.0m= 15.0sg= 15.0xa= 15.0xo= 15.1= 15.1gc= 15.1m= 15.1s= 15.1t= 15.1xb

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
Low
Authentication
None
Confidentiality
None
Integrity
None
Availability
Complete

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

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 Cisco IOS version
    Execute 'show version' on the device CLI and locate the version string in the output
    Affected if The version falls within 15.0 to 15.1 (including variants: 15.0, 15.0m, 15.0sg, 15.0xa, 15.0xo, 15.1, 15.1gc, 15.1m, 15.1s, 15.1t, 15.1xb)
  2. Check if IPS (Intrusion Prevention System) is enabled
    Execute 'show ip ips' or 'show module' to verify if IPS signatures and inspection are active
    Affected if IPS is configured and running on the device
  3. Check if Zone-Based Firewall (ZBFW) is configured
    Execute 'show zone-pair' or 'show policy-map type inspect' to verify ZBFW policies exist
    Affected if Zone-Based Firewall policies are configured on the device

A device is affected if it runs Cisco IOS version 15.0 through 15.1 AND has either IPS or ZBFW features enabled, making it vulnerable to memory exhaustion from rapid session creation.

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

Update Cisco IOS to a patched version beyond 15.1. If immediate update is not possible, consider rate-limiting session creation or temporarily disabling IPS/ZBFW features if not critical, while planning the upgrade.

Fix this in iOS Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,980
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Scan for this in your stack

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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-2011-3273 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