Is CVE-2016-4553 in the CISA KEV catalog?

No. CVE-2016-4553 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2016-4553?

CVE-2016-4553 has a CVSS v3 base score of 8.6 (HIGH).

What is the EPSS score for CVE-2016-4553?

CVE-2016-4553 has an EPSS score of 79.97% (100th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2016-4553?

Upgrade squid-cgi on ubuntu 14.04 to 3.3.8-1ubuntu6.8 or later. Fixes are available for 2 affected products.

CVE & CISA-KEV Catalog

CVE-2016-4553

HIGHEPSS 100th pctl

8.6

CVSS v3

NVD

Description

client_side.cc in Squid before 3.5.18 and 4.x before 4.0.10 does not properly ignore the Host header when absolute-URI is provided, which allows remote attackers to conduct cache-poisoning attacks via an HTTP request.

CWE-345

How to fix

Remediation Available

squid-cgiUbuntu

Fixed in:3.3.8-1ubuntu6.8USN-2995-1

Fixed in:3.5.12-1ubuntu7.2USN-2995-1

squid3Ubuntu

Fixed in:3.3.8-1ubuntu6.8USN-2995-1

Fixed in:3.5.12-1ubuntu7.2USN-2995-1

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeChanged

Impact

ConfidentialityNone

IntegrityHigh

AvailabilityNone

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

Exploit Intelligence

79.97%probability of exploitation in 30 days

100thpercentile

Very high risk: more likely to be exploited than 100% of all known CVEs.

References

Vendor Advisory2

Third-Party Advisory3

Other references8

Related Vulnerabilities

Other CWE-345 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-38831	High	7.8	98%	KEV + Ransom	Fix
CVE-2016-4554	High	8.6	39%	-	Fix
CVE-2023-35719	Medium	6.8	26%	-	-
CVE-2022-26871	Critical	9.8	20%	KEV	-
CVE-2014-4936	High	9.3	17%	-	-
CVE-2024-5458	Medium	5.3	12%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-06.