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CVE-2018-1000027

30
FAUCET Score

CVE-2018-1000027 is a NULL Pointer Dereference vulnerability in Squid HTTP Caching Proxy versions prior to 4.0.23, impacting various Canonical and Debian Linux distributions. This flaw allows a remote HTTP server to trigger a Denial of Service (DoS) for all proxy clients by responding with a crafted X-Forwarded-For header. With a CVSS score of 7.5 (High), the vulnerability is easily exploitable over the network without authentication or user interaction, leading to a complete loss of availability. Despite its high severity and ease of exploitation, there is no known active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 4.0.23CPE matchmatch criteria
cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:*
7.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:7.0:*:*:*:*:*:*:*
8.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
14.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*

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
12.91%
Probability of exploitation in next 30 days
EPSS Percentile
95.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.1291 is in the 94th percentile among its peer group of 51,506 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 (3)

redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: squid-7:3.5.20-15.el7
View patch
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: squid
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: squid34

Vendor Advisories (1)

redhatCVE-2018-1000027Moderate

squid: Incorrect pointer handling in HTTP processing and certificate download can lead to denial of service

Jan 19, 2018

References

github.com / squid-cache/squid/pull/129/files
Third Party Advisory
lists.debian.org / debian-lts-announce/2018/02/msg00001.html
Mailing ListThird Party Advisory
lists.debian.org / debian-lts-announce/2018/02/msg00002.html
Mailing ListThird Party Advisory
usn.ubuntu.com / 3557-1
Third Party Advisory
usn.ubuntu.com / 4059-2
debian.org / security/2018/dsa-4122
Third Party Advisory
squid-cache.org / Advisories/SQUID-2018_2.txt
PatchVendor Advisory
squid-cache.org / Versions/v3/3.5/changesets/SQUID-2018_2.patch
PatchVendor Advisory
squid-cache.org / Versions/v4/changesets/SQUID-2018_2.patch
PatchVendor Advisory