CVE-2020-25097Network attack vector

Security-control bypass via whitespace URL parsing

Published Mar 19, 2021 · Updated Aug 4, 2024

HTTP request smuggling in Squid 2.0 through 4.13 and 5.0.1 through 5.0.4 allows remote attackers to access services blocked by proxy controls. AnyP::Uri::parse fails to prefix path-rootless and path-noscheme request targets with a slash, allowing Squid and an origin server to disagree on request boundaries after URI whitespace handling. The client must be permitted by http_access, and uri_whitespace must be absent or set to allow, chop, or strip; the bounded result is unauthorized service access.

CVSS severity8.6
High
EPSS probability8.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP request smuggling in Squid 2.0 through 4.13 and 5.0.1 through 5.0.4 allows remote attackers to access services blocked by proxy controls. AnyP::Uri::parse fails to prefix path-rootless and path-noscheme request targets with a slash, allowing Squid and an origin server to disagree on request boundaries after URI whitespace handling. The client must be permitted by http_access, and uri_whitespace must be absent or set to allow, chop, or strip; the bounded result is unauthorized service access.

The record

CVE
CVE-2020-25097
Published
Mar 19, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1210
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 19, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.6Amazon LinuxCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
8.6OracleCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
8.6NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
5.0NVDAV:N/AC:L/Au:N/C:P/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1210Exploitation of Remote Services

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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