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CVE-2016-4553

69
FAUCET Score

CVE-2016-4553 is a cache-poisoning vulnerability affecting Squid versions before 3.5.18 and 4.x before 4.0.10, impacting various Linux distributions. This flaw arises from Squid's failure to properly ignore the Host header when an absolute-URI is provided in an HTTP request. With a CVSS score of 8.6 (HIGH), it presents a low-complexity network attack vector that can lead to high integrity impact, allowing attackers to manipulate cached content. Despite its high severity and EPSS score, there is no evidence of active exploitation, public exploit code, or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
12.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:12.04:*:*:*:lts:*:*:*
14.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*
15.10CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:15.10:*:*:*:*:*:*:*
16.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
<= 3.5.17CPE matchmatch criteria
cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

8.6HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
NONE
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
4.0
CvssVersion
3.0

Exploit Intelligence

EPSS Score
79.97%
Probability of exploitation in next 30 days
EPSS Percentile
99.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-25
Model: v2026.06.15
This CVE's current EPSS score of 0.7997 is in the 99th percentile among its peer group of 51,485 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: squid34-7:3.4.14-9.el6_8.3
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: squid-7:3.3.8-26.el7_2.3
View patch

Vendor Advisories (1)

redhatCVE-2016-4553Moderate

squid: Cache poisoning issue in HTTP Request handling

May 6, 2016

References

bugs.squid-cache.org / show_bug.cgi
Vendor Advisory
lists.opensuse.org / opensuse-security-announce/2016-08/msg00010.html
lists.opensuse.org / opensuse-security-announce/2016-08/msg00040.html
lists.opensuse.org / opensuse-updates/2016-08/msg00069.html
access.redhat.com / errata/RHSA-2016:1139
access.redhat.com / errata/RHSA-2016:1140
security.gentoo.org / glsa/201607-01
debian.org / security/2016/dsa-3625
oracle.com / technetwork/topics/security/linuxbulletinapr2016-2952096.html
Third Party Advisory
securitytracker.com / id/1035768
Third Party Advisory
squid-cache.org / Advisories/SQUID-2016_7.txt
Vendor Advisory
squid-cache.org / Versions/v3/3.5/changesets/squid-3.5-14039.patch
ubuntu.com / usn/USN-2995-1
Third Party Advisory