CVE-2011-4661Network attack vector

Service interruption via HTTP proxy memory leak

Published Feb 12, 2020 · Updated Nov 15, 2024

A memory leak in Cisco IOS before 15.2(1)T allows remote attackers to exhaust memory through the HTTP PROXY Server process. The process fails to release memory while handling traffic when Cisco ISR Web Security uses Cisco ScanSafe with NTLM user authentication. The affected features must be configured; memory exhaustion can interrupt device service without disclosing or altering data.

CVSS severity7.5
High
EPSS probability1.01%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A memory leak in Cisco IOS before 15.2(1)T allows remote attackers to exhaust memory through the HTTP PROXY Server process. The process fails to release memory while handling traffic when Cisco ISR Web Security uses Cisco ScanSafe with NTLM user authentication. The affected features must be configured; memory exhaustion can interrupt device service without disclosing or altering data.

The record

CVE
CVE-2011-4661
Published
Feb 12, 2020
Updated
Nov 15, 2024
Vendor
ClamAV
Product
Cisco IOS
Classifications
CWE-772, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 12, 2020CVE publishedPublication date reported by the CVE source.
  2. Nov 15, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=before 15.2(1)T

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco IOSversion=before 15.2(1)T

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-772Missing Release of Resource after Effective Lifetime
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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