CVE-2023-29406Public exploitNetwork attack vector

Downstream request injection via unvalidated Host header

Published Jul 11, 2023 · Updated Feb 13, 2025

HTTP request splitting in Go standard library net/http before 1.19.11 or 1.20.0 through 1.20.5 allows attackers to inject requests. Request.write places Request.Host or Request.URL.Host into the HTTP/1 Host line without rejecting CRLF control characters, allowing crafted values to become extra headers or requests. Exploitation requires an application to place unsanitized, untrusted data in a client request's Host field; the resulting traffic can alter downstream requests.

CVSS severity6.5
Medium
EPSS probability1.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP request splitting in Go standard library net/http before 1.19.11 or 1.20.0 through 1.20.5 allows attackers to inject requests. Request.write places Request.Host or Request.URL.Host into the HTTP/1 Host line without rejecting CRLF control characters, allowing crafted values to become extra headers or requests. Exploitation requires an application to place unsanitized, untrusted data in a client request's Host field; the resulting traffic can alter downstream requests.

The record

CVE
CVE-2023-29406
Published
Jul 11, 2023
Updated
Feb 13, 2025
Vendor
Go standard library
Product
net/http
Classifications
CWE-436, CWE-113, CAPEC-105
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 11, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 13, 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=0 <1.19.11
  2. Affected versionversion=1.20.0-0 <1.20.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Go standard library · net/httpversion=0 <1.19.11; version=1.20.0-0 <1.20.6

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/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 exploitPublished

Weakness, pattern, technique

CWE-436Interpretation Conflict
CWE-113Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
CAPEC-105HTTP Request Splitting

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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