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Squid CVE-2025-54574

CRITICAL
Heap-based Buffer Overflow (CWE-122)
2025-08-01 security-advisories@github.com
RCE Buffer Overflow Heap Overflow Red Hat Suse Squid Squid Cache
9.3
CVSS 3.1 · GitHub Advisory
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Vulnerability Assessment

Weakness
CWE
CWE-122
OWASP Top 10:2025
A06:2021 - Vulnerable and Outdated Components
ASVS 5.0
V15 - Secure Coding and Architecture Heap buffer bounds checking
MITRE ATT&CK

1 technique across 1 tactic: Execution

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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Impact

CVSS score of 9.3 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. EPSS exploitation probability: 2.96%.
Exploit ScenarioDerived

This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the critical-severity affected system.
This Week Schedule remediation this week. Why: CRITICAL severity.
Patch available 3.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 28, 2026

Squid is a caching proxy for the Web. Rated critical severity (CVSS 9.3), 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. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

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Technical ContextAI · show details

This vulnerability is classified under CWE-122. Squid is a caching proxy for the Web. In versions 6.3 and below, Squid is vulnerable to a heap buffer overflow and possible remote code execution attack when processing URN due to incorrect buffer management. This has been fixed in version 6.4. To work around this issue, disable URN access permissions. Affected products include: Squid-Cache Squid. Version information: version 6.4..

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

GitHub Advisory PRIMARY 9.3 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:H
SUSE CRITICAL
Red Hat 8.9 HIGH

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
Low
Availability
High

Lifecycle Timeline

2
Patch released
Mar 28, 2026 - 19:04 nvd
Patch available
CVE Published
Aug 01, 2025 - 18:15 nvd
CRITICAL 9.3

DescriptionGitHub Advisory

Squid is a caching proxy for the Web. In versions 6.3 and below, Squid is vulnerable to a heap buffer overflow and possible remote code execution attack when processing URN due to incorrect buffer management. This has been fixed in version 6.4. To work around this issue, disable URN access permissions.

Executive ViewAI

Why It Matters

Organizations using Squid face critical risk from CVE-2025-54574, a heap-based buffer overflow vulnerability rated CVSS 9.3. Exploitation could allow attackers to corrupt memory, crash the application, or potentially execute arbitrary code. A patch is available and should be applied immediately given the critical severity.

Business Impact: Severe
Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Enable ASLR and DEP where available; (2) Implement network segmentation; (3) Monitor for exploitation indicators.

Threat Intelligence Overview

EPSS Score
3.0%
Top 14% exploitable

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.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC No
EPSS 3.0%
Patch available Yes
Active threat No
Deciding rule
CRITICAL severity
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Out-of-Cycle
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact
Very High

Priority Score

49
Low Medium High Critical
KEV: 0
EPSS: +3
CVSS: +46
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Buffer Overflow HIGH

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

Heap Overflow HIGH

A heap overflow occurs when a program writes data beyond the bounds of a buffer allocated in the heap memory region.

Remote Code Execution CRITICAL

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

Affected Products (CPE)GitHub Advisory

cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:*

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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
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Squid is vulnerable to a Denial of Service, where a remote attacker can perform buffer overflow attack by writing up to

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8.1 Apr 25

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
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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
CVE-2016-3947 HIGH
8.2 Apr 07

Heap-based buffer overflow in the Icmp6::Recv function in icmp/Icmp6.cc in the pinger utility in Squid before 3.5.16 and
CVE-2013-4123 MEDIUM POC
5.0 Sep 16

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

CVE-2013-4115 HIGH
7.5 Aug 09

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

CVE-2016-4554 HIGH
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mime_header.cc in Squid before 3.5.18 allows remote attackers to bypass intended same-origin restrictions and possibly c
CVE-2014-7141 MEDIUM
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The pinger in Squid 3.x before 3.4.8 allows remote attackers to obtain sensitive information or cause a denial of servic
CVE-2014-3609 MEDIUM
5.0 Sep 11

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 (
CVE-2016-2569 HIGH
7.5 Feb 27

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
CVE-2016-3948 HIGH
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Squid 3.x before 3.5.16 and 4.x before 4.0.8 improperly perform bounds checking, which allows remote attackers to cause

Same weakness CWE-122 – Heap-based Buffer Overflow

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CVE-2022-47966 CRITICAL POC
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CVE-2012-4681 CRITICAL POC
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CVE-2023-3519 CRITICAL POC
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CVE-2015-5119 CRITICAL POC
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CVE-2016-4117 CRITICAL POC
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CVE-2015-3113 CRITICAL POC
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Vendor StatusVendor

SUSE

Severity: Critical
Product Status
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed
SUSE Linux Enterprise Module for Server Applications 15 SP7 Fixed
SUSE Linux Enterprise Server 15 SP7 Fixed
SUSE Linux Enterprise Server 16.1 Fixed
SUSE Linux Enterprise Server for SAP Applications 15 SP7 Fixed

References

Advisories & patches
PATCH https://github.com/squid-cache/squid/commit/a27bf4b84da23594150c7a86a23435df0b35b988 PATCH https://github.com/squid-cache/squid/security/advisories/GHSA-w4gv-vw3f-29g3 ADVISORY https://access.redhat.com/errata/RHSA-2023:7465 ADVISORY https://access.redhat.com/errata/RHSA-2023:7668 ADVISORY https://access.redhat.com/errata/RHSA-2024:0072 ADVISORY https://access.redhat.com/errata/RHSA-2024:0397 ADVISORY https://access.redhat.com/errata/RHSA-2024:0771 ADVISORY https://access.redhat.com/errata/RHSA-2024:0772 ADVISORY https://access.redhat.com/errata/RHSA-2024:0773 ADVISORY https://access.redhat.com/errata/RHSA-2024:1153 ADVISORY https://access.redhat.com/errata/RHSA-2025:14414 ADVISORY https://vuldb.com/vuln/318528 REF http://www.openwall.com/lists/oss-security/2025/11/05/5 REF https://github.com/squid-cache/squid/releases/tag/SQUID_6_4 REF https://lists.debian.org/debian-lts-announce/2025/09/msg00027.html

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