CVE-2018-1000027: n/a vulnerability

CVE-2018-1000027: The Squid Software Foundation Squid HTTP Caching Proxy version prior to version 4.0.23 contains a NULL Poin...

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.

UnknownCVSS not scoredNot KEV-listedUpdatedAug 5, 2024, 12:33 UTC (UTC+00:00)

Security readout for executives and security teams

This vulnerability can crash a Squid web proxy when it processes a crafted X-Forwarded-For response header from a remote HTTP server. The main business risk is loss of proxy service for users relying on it for web access. The source bundle says it was fixed in Squid 4.0.23 and later. Exposure is likely where Squid versions before 4.0.23, or unpatched distribution builds, proxy user traffic to arbitrary remote HTTP servers. The bundle does not provide complete CPEs or exact distro package versions. Treat this as a service availability issue for shared web proxy infrastructure. Patch promptly if Squid is on user egress paths, because one affected proxy outage can disrupt many clients, but available sources do not show code execution or confirmed active exploitation. Mitigation focus: Upgrade Squid to 4.0.23 or later where applicable.; Apply Debian or Ubuntu vendor security updates for supported Squid packages.; Check Squid advisory SQUID-2018_2 for upstream guidance..

Prepared: Jun 7, 2026, 20:58 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Vulnerability profileCVE Program record

Severity: Unknown
CVSS: Not scored
Known Exploited: No
Published: Feb 9, 2018, 23:00 UTC (UTC+00:00)

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors

0Timeline events

0ADP providers

7Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

CVE List V5 sourceCVE List V5
USN-3557-1CVE reference · vendor-advisory, x_refsource_UBUNTU
DSA-4122CVE reference · vendor-advisory, x_refsource_DEBIAN
[debian-lts-announce] 20180202 [SECURITY] [DLA 1266-1] squid3 security updateCVE reference · mailing-list, x_refsource_MLIST
https://github.com/squid-cache/squid/pull/129/filesCVE reference · x_refsource_CONFIRM
[debian-lts-announce] 20180202 [SECURITY] [DLA 1267-1] squid security updateCVE reference · mailing-list, x_refsource_MLIST
USN-4059-2CVE reference · vendor-advisory, x_refsource_UBUNTU

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus

n/an/an/aListed

Weakness

CWE details

No CWE listed

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