CVE-2024-1135Network attack vector

Restricted-endpoint access via conflicting Transfer-Encoding headers

Published Apr 16, 2024 · Updated Feb 13, 2025

HTTP request smuggling in Gunicorn before 22.0.0 allows remote attackers to access restricted endpoints via crafted HTTP requests. The HTTP message parser treats a chunked Transfer-Encoding header as authoritative even when multiple headers conflict or chunked is not the final coding. Exploitation requires a network path that forwards invalid requests, enabling security-control bypass and exposure or manipulation of protected application data.

CVSS severity7.5
High
EPSS probability3.00%
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 Gunicorn before 22.0.0 allows remote attackers to access restricted endpoints via crafted HTTP requests. The HTTP message parser treats a chunked Transfer-Encoding header as authoritative even when multiple headers conflict or chunked is not the final coding. Exploitation requires a network path that forwards invalid requests, enabling security-control bypass and exposure or manipulation of protected application data.

The record

CVE
CVE-2024-1135
Published
Apr 16, 2024
Updated
Feb 13, 2025
Vendor
Benoît Chesneau
Product
Gunicorn
Classifications
CWE-444, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 16, 2024CVE 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=*
  2. Affected versionversion=unspecified <=latest

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Benoît Chesneau · Gunicornversion=*; version=unspecified <=latest

Published CVSS scores

7.5Protect AICVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
8.2GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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 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

CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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