CVE-2024-23638Public exploitNetwork attack vector

Service crash via continued processing after write errors

Published Jan 23, 2024 · Updated Jun 17, 2025

Expired pointer dereference in Squid before 6.6 allows remote authenticated users to crash the proxy through Cache Manager error responses. After a client write failure, Server::clientWriteDone calls afterClientWrite instead of terminating all transactions, allowing a null reply to reach Http::One::Server::handleReply and trigger an assertion. Cache Manager access must be permitted to the client; successful exploitation aborts Squid and interrupts proxy service.

CVSS severity6.5
Medium
EPSS probability60.05%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Expired pointer dereference in Squid before 6.6 allows remote authenticated users to crash the proxy through Cache Manager error responses. After a client write failure, Server::clientWriteDone calls afterClientWrite instead of terminating all transactions, allowing a null reply to reach Http::One::Server::handleReply and trigger an assertion. Cache Manager access must be permitted to the client; successful exploitation aborts Squid and interrupts proxy service.

The record

CVE
CVE-2024-23638
Published
Jan 23, 2024
Updated
Jun 17, 2025
Vendor
The Squid Software Foundation
Product
Squid
Classifications
CWE-825, CWE-672, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 23, 2024CVE publishedPublication date reported by the CVE source.
  2. Jun 17, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 6.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

The Squid Software Foundation · Squidversion=< 6.6

Published CVSS scores

6.5GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.5NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-825Expired Pointer Dereference
CWE-672Operation on a Resource after Expiration or Release
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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