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CVE-2016-4555

51
FAUCET Score

CVE-2016-4555 is a denial-of-service vulnerability affecting Squid 3.x before 3.5.18 and 4.x before 4.0.10, allowing remote servers to crash the proxy via crafted Edge Side Includes (ESI) responses. With a CVSS score of 7.5 (High), it can be exploited remotely with low complexity, requiring no user interaction or privileges, leading to a complete loss of availability. 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.

Impacted Technologies

VendorProductVersion(s)CPE
3.0CPE matchmatch criteria
cpe:2.3:a:squid-cache:squid:3.0:*:*:*:*:*:*:*
3.1CPE matchmatch criteria
cpe:2.3:a:squid-cache:squid:3.1:*:*:*:*:*:*:*
3.1.0.1CPE matchmatch criteria
cpe:2.3:a:squid-cache:squid:3.1.0.1:*:*:*:*:*:*:*
3.1.0.2CPE matchmatch criteria
cpe:2.3:a:squid-cache:squid:3.1.0.2:*:*:*:*:*:*:*
3.1.0.3CPE matchmatch criteria
cpe:2.3:a:squid-cache:squid:3.1.0.3:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

7.5HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.0

Exploit Intelligence

EPSS Score
53.92%
Probability of exploitation in next 30 days
EPSS Percentile
98.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.5392 is in the 98th 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-2016-4555Moderate

squid: SegFault from ESIInclude::Start

May 6, 2016

References

bugs.squid-cache.org / show_bug.cgi
ExploitIssue TrackingPatchVendor 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
openwall.com / lists/oss-security/2016/05/06/3
PatchRelease Notes
openwall.com / lists/oss-security/2016/05/06/5
PatchThird Party Advisory
oracle.com / technetwork/topics/security/linuxbulletinapr2016-2952096.html
Third Party Advisory
securitytracker.com / id/1035770
Third Party Advisory
squid-cache.org / Advisories/SQUID-2016_9.txt
Vendor Advisory
squid-cache.org / Versions/v3/3.4/changesets/SQUID-2016_9.patch
Patch
squid-cache.org / Versions/v3/3.5/changesets/SQUID-2016_9.patch
Patch
ubuntu.com / usn/USN-2995-1
Third Party Advisory