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CVE-2018-1000027· NVD / CVE Program· CNA mitre

The Squid Software Foundation Squid HTTP Caching Proxy version prior to version 4.0.23 contains a NULL Pointer Dereference vulnerability in

Noroxi assessment

Priority: Monitor (action score 34/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 12.9% (FIRST EPSS); higher than 96.2% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: n/a n/a 4.0.23.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to n/a n/a 4.0.23 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

The Squid Software Foundation Squid HTTP Caching Proxy version prior to version 4.0.23 contains a NULL Pointer Dereference vulnerability in HTTP Response X-Forwarded-For header processing that can result in Denial of Service to all clients of the proxy. This attack appear to be exploitable via Remote HTTP server responding with an X-Forwarded-For header to certain types of HTTP request. This vulnerability appears to have been fixed in 4.0.23 and later.

HighCVSS 7.5 · v3.0—No exploit Fix available
Published
Feb 9, 2018
Updated
Jun 16, 2026
EPSS
12.9% · 96th percentile

Report tools

JSON

Action score

34

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
4 / 30 · 12.9%

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
squid-cachesquid
debiandebian linux
canonicalubuntu linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • canonical ubuntu linux14.04
  • canonical ubuntu linux16.04
  • canonical ubuntu linux17.10
  • debian debian linux7.0
  • debian debian linux8.0
  • debian debian linux9.0
  • squid-cache squidbefore 4.0.23

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Alpine:v3.10squidbefore 3.5.27-r23.5.27-r2
Alpine:v3.4squidbefore 3.5.27-r03.5.27-r0
Debian:12squidbefore 4.1-14.1-1
Debian:7squidbefore 2.7.STABLE9-4.1+deb7u32.7.STABLE9-4.1+deb7u3
Debian:7squid3before 3.1.20-2.2+deb7u83.1.20-2.2+deb7u8
Debian:8squid3before 3.4.8-6+deb8u53.4.8-6+deb8u5
Debian:9squid3before 3.5.23-5+deb9u13.5.23-5+deb9u1
openSUSE:Tumbleweedsquidbefore 4.16-1.54.16-1.5
Red Hat:enterprise_linux:7::serversquidbefore 7:3.5.20-15.el77:3.5.20-15.el7
Red Hat:enterprise_linux:7::serversquid-debuginfobefore 7:3.5.20-15.el77:3.5.20-15.el7
Red Hat:enterprise_linux:7::serversquid-migration-scriptbefore 7:3.5.20-15.el77:3.5.20-15.el7
Red Hat:enterprise_linux:7::serversquid-sysvinitbefore 7:3.5.20-15.el77:3.5.20-15.el7
SUSE:Linux Enterprise Server 11 SP4squid3before 3.1.23-8.16.37.3.13.1.23-8.16.37.3.1
SUSE:Linux Enterprise Server for Raspberry Pi 12 SP2squidbefore 3.5.21-26.6.13.5.21-26.6.1

Same product

squid-cache: all records

Other highest-scoring records for the same primary product.

  • CVE-2023-46847Squid: denial of service in http digest authentication
    57Plan
  • CVE-2024-25617Denial of Service in HTTP Header parser in squid proxy
    56Plan
  • CVE-2023-49285Denial of Service in HTTP Message Processing in Squid
    56Plan
  • CVE-2021-31806An issue was discovered in Squid before 4.15 and 5.x before 5.0.6.
    55Plan
  • CVE-2020-8450An issue was discovered in Squid before 4.10.
    51Plan
  • CVE-2024-25111SQUID-2024:1 Denial of Service in HTTP Chunked Decoding
    50Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
n/a n/a4.0.23 · descriptionVendor (CNA)
alpine:squid3.5.27-r2 · Alpine:v3.10Package registry (OSV)
debian:squid4.1-1 · Debian:12Package registry (OSV)
debian:squid33.1.20-2.2+deb7u8 · Debian:7Package registry (OSV)
opensuse:squid4.16-1.5 · openSUSE:TumbleweedPackage registry (OSV)
red hat:squid7:3.5.20-15.el7 · Red Hat:enterprise_linux:7::serverPackage registry (OSV)
red hat:squid-debuginfo7:3.5.20-15.el7 · Red Hat:enterprise_linux:7::serverPackage registry (OSV)
red hat:squid-migration-script7:3.5.20-15.el7 · Red Hat:enterprise_linux:7::serverPackage registry (OSV)
red hat:squid-sysvinit7:3.5.20-15.el7 · Red Hat:enterprise_linux:7::serverPackage registry (OSV)
suse:squid3.5.21-26.6.1 · SUSE:Linux Enterprise Server for Raspberry Pi 12 SP2Package registry (OSV)
suse:squid33.1.23-8.16.37.3.1 · SUSE:Linux Enterprise Server 11 SP4Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-476 · NULL Pointer Dereference

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (8 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records