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iOSOperating system · Cisco

CVE-2011-4019

MEDIUM · 5.4 CVSS v2.0 Published 2012-05-03
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
63/100
Remediation priority · Elevated
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 12.4 and 15.0 through 15.2, and Cisco Unified Communications Manager (CUCM) 7.x, allows remote attackers to cause a denial of service (memory consumption) via a crafted response to a SIP SUBSCRIBE message, aka Bug IDs CSCto93837 and CSCtj61883.

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

Memory leak in Cisco IOS and CUCM SIP SUBSCRIBE message handling. When processing a crafted response to a SIP SUBSCRIBE request, the device fails to properly deallocate memory, causing progressive memory consumption until the system becomes unresponsive.

MitigationApply Cisco security patches for Bug IDs CSCto93837 and CSCtj61883, or upgrade to patched IOS/CUCM versions. As interim workarounds, implement SIP traffic filtering or rate limiting on perimeter devices to block malicious SUBSCRIBE responses.

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:= 12.4= 15.0= 15.1= 15.2
Unified Communications ManagerApplication
Affected:= 7.0= 7.0\(1\)= 7.0\(1\)su1= 7.0\(1\)su1a= 7.0\(2\)= 7.0\(2a\)= 7.0\(2a\)su1= 7.0\(2a\)su2= 7.0_base= 7.1= 7.1\(2a\)= 7.1\(2a\)su1

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
High
Authentication
None
Confidentiality
None
Integrity
None
Availability
Complete

AV:N/AC:H/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 Cisco product type
    Determine whether the device runs Cisco IOS (IOS, IOS-XE) or Cisco Unified Communications Manager (CUCM). For IOS devices, use 'show version' command. For CUCM, check the About page in the Administration interface or run 'utils system version' from the CLI.
    Affected if Product type is Cisco IOS or CUCM but version cannot be determined or is unknown
  2. Check IOS version against affected releases
    For IOS devices, run 'show version' and examine the firmware version. Compare against affected versions: 12.4, 15.0, 15.1, 15.2. Note that only versions exactly matching these release trains are affected (for example, 15.2(4)E is NOT in the list).
    Affected if IOS version is exactly 12.4, 15.0, 15.1, or 15.2 train (not point releases like 15.2(4)E)
  3. Check CUCM version against affected releases
    For CUCM, access the Cisco Unified Communications Manager Administration page and go to About > Version, or use the CLI command 'utils system version'. Compare against affected versions: 7.0, 7.0(1), 7.0(1)su1, 7.0(1)su1a, 7.0(2), 7.0(2a), 7.0(2a)su1, 7.0(2a)su2, 7.0_base, 7.1, 7.1(2a), 7.1(2a)su1.
    Affected if CUCM version exactly matches one of the listed affected 7.x versions
  4. Verify SIP SUBSCRIBE is enabled
    For IOS: run 'show sip-ua status' or 'show running-config | include sip' to check if SIP user agent is configured. For CUCM: check under Cisco Unified Communications Manager Administration > System > Security > SIP Trunk Security Profile, or verify SIP trunks exist in Device > Trunk. The vulnerability requires SIP SUBSCRIBE handling to be active.
    Affected if SIP is not configured or SIP SUBSCRIBE handling is not enabled (vulnerability does not apply)
  5. Monitor for memory leak symptoms
    For IOS: run 'show memory summary' or 'show memory history' over time to observe progressive memory consumption in the SIP process. For CUCM: monitor using RTMT (Real Time Monitoring Tool) for Java heap or system memory growth, particularly in the SIP process.
    Affected if Device shows unexplained progressive memory consumption tied to SIP processing after sustained SUBSCRIBE traffic

System is likely affected if it runs IOS version 12.4/15.0/15.1/15.2 or CUCM version 7.x (as listed) AND has SIP SUBSCRIBE functionality enabled, with memory consumption increasing during SIP SUBSCRIBE message processing.

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

Apply Cisco security patches for Bug IDs CSCto93837 and CSCtj61883, or upgrade to patched IOS/CUCM versions. As interim workarounds, implement SIP traffic filtering or rate limiting on perimeter devices to block malicious SUBSCRIBE responses.

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-2011-4019 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