CVE-2020-10109Public exploitNetwork attack vector

Request smuggling via conflicting message-length headers

Published Mar 12, 2020 · Updated Aug 4, 2024

HTTP request smuggling in Twisted Web before 20.3.0 allows remote attackers to inject pipelined requests via conflicting HTTP headers. The HTTP parser gives Content-Length precedence over Transfer-Encoding: chunked, causing the remaining body bytes to be parsed as another request. Exploitation requires a reachable HTTP/1.1 service that accepts a persistent connection; effects such as filter bypass, cache poisoning, or session interference depend on the surrounding infrastructure.

CVSS severity9.8
Critical
EPSS probability3.29%
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 Twisted Web before 20.3.0 allows remote attackers to inject pipelined requests via conflicting HTTP headers. The HTTP parser gives Content-Length precedence over Transfer-Encoding: chunked, causing the remaining body bytes to be parsed as another request. Exploitation requires a reachable HTTP/1.1 service that accepts a persistent connection; effects such as filter bypass, cache poisoning, or session interference depend on the surrounding infrastructure.

The record

CVE
CVE-2020-10109
Published
Mar 12, 2020
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-444, CAPEC-33, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 12, 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 privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.3GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P

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 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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