Squid
CVE-2018-1000027
HIGH
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A10:2025 - Mishandling of Exceptional Conditions
ASVS 5.0
V16 - Security Logging and Error Handling Null pointer safety, defensive checks
MITRE ATT&CK
1 technique across 1 tactic: Impact The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Impact | CVSS score of 7.5 (HIGH). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. |
| Exploit ScenarioDerived | A remote attacker could crash the application by dereferencing a null pointer by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability. |
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Alert meAnalysisAI
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. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.
RemediationAI
A vendor patch is available. Apply the latest security update as soon as possible. Check pointers before dereferencing. Use static analysis tools to detect null pointer paths.
Affects your stack
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Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This vulnerability is classified as NULL Pointer Dereference (CWE-476), which allows attackers to crash the application by dereferencing a null pointer. 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. Affected products include: Squid-Cache Squid, Debian Debian Linux, Canonical Ubuntu Linux. Version information: version 4.0.23.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
DescriptionNVD
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.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
A null pointer dereference occurs when a program attempts to access memory through a pointer that has been set to NULL (address 0x0).
Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.
Affected Products (CPE)NVD
client_side.cc in Squid before 3.5.18 and 4.x before 4.0.10 does not properly ignore the Host header when absolute-URI i
Squid is vulnerable to a Denial of Service, where a remote attacker can perform buffer overflow attack by writing up to
Buffer overflow in Squid 3.x before 3.5.17 and 4.x before 4.0.9 allows remote attackers to execute arbitrary code via cr
client_side_request.cc in Squid 3.x before 3.5.18 and 4.x before 4.0.10 allows remote servers to cause a denial of servi
Heap-based buffer overflow in the Icmp6::Recv function in icmp/Icmp6.cc in the pinger utility in Squid before 3.5.16 and
client_side_request.cc in Squid 3.2.x before 3.2.13 and 3.3.x before 3.3.8 allows remote attackers to cause a denial of
Buffer overflow in the idnsALookup function in dns_internal.cc in Squid 3.2 through 3.2.11 and 3.3 through 3.3.6 allows
mime_header.cc in Squid before 3.5.18 allows remote attackers to bypass intended same-origin restrictions and possibly c
The pinger in Squid 3.x before 3.4.8 allows remote attackers to obtain sensitive information or cause a denial of servic
HttpHdrRange.cc in Squid 3.x before 3.3.12 and 3.4.x before 3.4.6 allows remote attackers to cause a denial of service (
Squid 3.x before 3.5.15 and 4.x before 4.0.7 does not properly append data to String objects, which allows remote server
Squid 3.x before 3.5.16 and 4.x before 4.0.8 improperly perform bounds checking, which allows remote attackers to cause
Exploit-DB