What is CVE-2011-4661?

CVE-2011-4661 is a high-severity vulnerability in Cisco iOS, classified under Missing Release of Resource after Effective Lifetime. CVSS score: 7.5/10. Published 2020-02-12.

How severe is CVE-2011-4661?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Cisco iOS

CVE-2011-4661

A memory leak vulnerability exists in Cisco IOS before 15.2(1)T due to a memory leak in the HTTP PROXY Server process (aka CSCtu52820), when configured with Cisco ISR Web Security with Cisco ScanSafe and User Authenticaiton NTLM configured.

Published 2020-02-12 · last modified 2026-06-16.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.010 (61.8th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 62nd percentile — 61.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.010 · newest: 0.010 · change: 0.000

Affected products

Cisco iOS — versions before 15.2(1)T

Weakness classification (CWE)

CWE-772 — Missing Release of Resource after Effective Lifetime

References

www.cisco.com/c/en/us/td/docs/ios/15_2m_and_t/release/notes/15_2m_and_t/152-1TC… (Vendor Advisory)

Frequently asked questions

What is CVE-2011-4661?: CVE-2011-4661 is a high-severity vulnerability in Cisco iOS, classified under Missing Release of Resource after Effective Lifetime. CVSS score: 7.5/10. Published 2020-02-12.
How severe is CVE-2011-4661?: High severity. CVSS v3 base score is 7.5 out of 10.