CVE-2020-15049Public exploitNetwork attack vector

Cache poisoning via malformed Content-Length prefixes

Published Jun 30, 2020 · Updated Aug 4, 2024

HTTP request smuggling in Squid before 4.12 and 5.x before 5.0.3 allows remote authenticated users to poison its HTTP cache. ContentLengthInterpreter passes signed or non-OWS-prefixed Content-Length values to numeric parsing instead of rejecting the invalid prefixes. The user must be a trusted proxy client, and an upstream server must interpret the smuggled request and generate the poison response sequence.

CVSS severity9.9
Critical
EPSS probability5.71%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP request smuggling in Squid before 4.12 and 5.x before 5.0.3 allows remote authenticated users to poison its HTTP cache. ContentLengthInterpreter passes signed or non-OWS-prefixed Content-Length values to numeric parsing instead of rejecting the invalid prefixes. The user must be a trusted proxy client, and an upstream server must interpret the smuggled request and generate the poison response sequence.

The record

CVE
CVE-2020-15049
Published
Jun 30, 2020
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-444, CAPEC-33, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 30, 2020CVE 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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:P
9.9MITRECVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/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-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
CAPEC-33HTTP Request Smuggling
T1190Exploit Public-Facing Application

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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