CVE-2023-46728VulnerabilityPublished 6 Nov 2023Updated 3 Nov 2025

CVE-2023-46728: squid · NULL Pointer Dereference

Affects squidSource CVE Database V5

Not known to be exploited · CVSS 7.5 High : upgrade to 6.0.1 soon.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 5.9% chance of exploitation in 30 days – higher than 93% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 6.0.1

CVSS:3.1/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: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 6 Nov 2023
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade squid-cache/squid to 6.0.1.

Affected software

Product	Affected	Fixed in
GitHubsquid-cache/squid`pkg:github/squid-cache/squid`Other threats	Affected <6.0.1	Fixed in 6.0.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

1. Upgrade Squid to version 6.0.1 or later, which removes Gopher support and fixes the vulnerability. 2. If immediate upgrade is not feasible, configure Squid to reject or block all Gopher protocol URL requests to prevent triggering the NULL pointer dereference. This can be done by adjusting access control lists (ACLs) or filtering rules to deny gopher:// URLs. 3. Monitor network traffic for unusual Gopher protocol requests or spikes that could indicate exploitation attempts. 4. Implement network-level filtering to block outbound and inbound Gopher traffic where it is not required, reducing exposure. 5. Regularly audit proxy configurations and logs to detect potential crashes or service interruptions related to this vulnerability. 6. Plan for timely patch management and vulnerability scanning to identify and remediate outdated Squid installations. 7. Educate network administrators about the risks associated with legacy protocols like Gopher and the importance of disabling unused services. These targeted steps go beyond generic advice by focusing on protocol-specific controls and operational monitoring.

Description

Squid is a caching proxy for the Web supporting HTTP, HTTPS, FTP, and more. Due to a NULL pointer dereference bug Squid is vulnerable to a Denial of Service attack against Squid's Gopher gateway. The gopher protocol is always available and enabled in Squid prior to Squid 6.0.1. Responses triggering this bug are possible to be received from any gopher server, even those without malicious intent. Gopher support has been removed in Squid version 6.0.1. Users are advised to upgrade. Users unable to upgrade should reject all gopher URL requests.

Impact

For European organizations, the primary impact of CVE-2023-46728 is the potential for denial of service on Squid proxy servers, which are widely used for web caching, content filtering, and access control. Disruption of Squid services can degrade network performance, interrupt user access to web resources, and impact business continuity. This is particularly critical for organizations relying on Squid proxies as a central component of their network infrastructure, including ISPs, educational institutions, government agencies, and enterprises. Since the vulnerability can be triggered remotely without authentication, attackers can cause service outages with minimal effort. Although no data confidentiality or integrity loss occurs, availability degradation can lead to operational disruptions and increased support costs. European organizations with strict uptime requirements or regulatory obligations for service availability must address this vulnerability promptly. The removal of Gopher support in newer versions also reduces attack surface, but legacy systems remain at risk if not updated or properly configured.

CWE-476NULL Pointer Dereference (opens in a new tab)
Base weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #13OWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product dereferences a pointer that it expects to be valid but is NULL.
Implementation
For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
Requirements
Select a programming language that is not susceptible to these issues.
Implementation
Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 3 Nov 2025, 18:47 UTC

WeaknessesCWE-476

Technical details

References

Community reviews

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