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CVE-2016-4554

45
FAUCET Score

CVE-2016-4554 describes a header smuggling vulnerability in Squid versions prior to 3.5.18, affecting various Linux distributions including Canonical and Oracle. This flaw allows remote attackers to bypass same-origin restrictions and potentially conduct cache-poisoning attacks through a crafted HTTP Host header. With a CVSSv3 score of 8.6 (HIGH), it has a network attack vector, low attack complexity, and high integrity impact, but no confidentiality or availability impact. Despite its high severity and FAUCET Risk Score of 98/100, there is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
6CPE matchmatch criteria
cpe:2.3:o:oracle:linux:6:*:*:*:*:*:*:*
7CPE matchmatch criteria
cpe:2.3:o:oracle:linux:7:*:*:*:*:*:*:*
<= 3.5.17CPE matchmatch criteria
cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:*
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:*:*:*

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
38.89%
Probability of exploitation in next 30 days
EPSS Percentile
98.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-24
Model: v2026.06.15
This CVE's current EPSS score of 0.3889 is in the 97th percentile among its peer group of 51,466 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 (4)

redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: squid-7:3.1.23-16.el6_8.4
View patch
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
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 5Fixed in: squid

Vendor Advisories (1)

redhatCVE-2016-4554Moderate

squid: Header Smuggling issue in HTTP Request processing

May 6, 2016

References

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-2016:1138
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/1035769
Third Party Advisory
squid-cache.org / Advisories/SQUID-2016_8.txt
Vendor Advisory
squid-cache.org / Versions/v3/3.1/changesets/SQUID-2016_8.patch
Patch
squid-cache.org / Versions/v3/3.2/changesets/SQUID-2016_8.patch
Patch
squid-cache.org / Versions/v3/3.3/changesets/SQUID-2016_8.patch
Patch
squid-cache.org / Versions/v3/3.4/changesets/SQUID-2016_8.patch
Patch
squid-cache.org / Versions/v3/3.5/changesets/SQUID-2016_8.patch
Patch
ubuntu.com / usn/USN-2995-1
Third Party Advisory