CVE-2025-54574Network attack vector

Remote code execution via fixed-size URN buffer

Published Aug 1, 2025 · Updated Nov 5, 2025

Heap buffer overflow in Squid before 6.4 allows remote attackers to execute code through a crafted URN Trivial-HTTP response. urnHandleReply passes a fixed 4 KB destination to storeClientCopy while mixing serialized header and body offsets, allowing response data to exceed its buffer accounting. The remote server must answer a proxy-initiated URN resolution request; exploitation can also disclose up to 4 KB of heap data, including credentials.

CVSS severity9.3
Critical
EPSS probability22.67%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer overflow in Squid before 6.4 allows remote attackers to execute code through a crafted URN Trivial-HTTP response. urnHandleReply passes a fixed 4 KB destination to storeClientCopy while mixing serialized header and body offsets, allowing response data to exceed its buffer accounting. The remote server must answer a proxy-initiated URN resolution request; exploitation can also disclose up to 4 KB of heap data, including credentials.

The record

CVE
CVE-2025-54574
Published
Aug 1, 2025
Updated
Nov 5, 2025
Vendor
The Squid Software Foundation
Product
Squid
Classifications
CWE-122, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 1, 2025CVE publishedPublication date reported by the CVE source.
  2. Nov 5, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=< 6.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Squid Software Foundation · Squidversion=< 6.4

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.3GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:H
6.8Amazon LinuxCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

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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