CVE-2020-7658Public exploitNetwork attack vector

Request smuggling via ambiguous HTTP framing

Published May 22, 2020 · Updated Aug 4, 2024

HTTP request smuggling in Yutaka Matsubara Meinheld before 1.0.2 allows remote attackers to desynchronize proxied HTTP requests. Its parser accepts conflicting Content-Length fields, treats the final value as authoritative, and also accepts invalid Transfer-Encoding combinations. Exploitation requires a front-end intermediary that frames the same persistent connection differently, enabling cache poisoning, request routing bypass, or disclosure of another user's request data.

CVSS severity6.1
Medium
EPSS probability0.69%
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 Yutaka Matsubara Meinheld before 1.0.2 allows remote attackers to desynchronize proxied HTTP requests. Its parser accepts conflicting Content-Length fields, treats the final value as authoritative, and also accepts invalid Transfer-Encoding combinations. Exploitation requires a front-end intermediary that frames the same persistent connection differently, enabling cache poisoning, request routing bypass, or disclosure of another user's request data.

The record

CVE
CVE-2020-7658
Published
May 22, 2020
Updated
Aug 4, 2024
Vendor
Yutaka Matsubara
Product
Meinheld
Classifications
CWE-444, CAPEC-33, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 22, 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?

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

  1. Affected versionversion=All versions prior to 1.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Yutaka Matsubara · Meinheldversion=All versions prior to 1.0.2

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
5.3GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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 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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