CVE-2022-24761Network attack vector

Request smuggling via lax length and extension parsing

Published Mar 17, 2022 · Updated Apr 23, 2025

HTTP request smuggling in Pylons Project Waitress before 2.1.1 allows remote attackers to inject requests through a permissive proxy. The request parser passed unvalidated Content-Length and chunk-size strings to Python int(), while ChunkedReceiver discarded invalid chunk extensions. Exploitation requires a front-end proxy that interprets the malformed framing differently, allowing attacker-chosen HTTP messages to reach later application processing.

CVSS severity8.7
High
EPSS probability1.78%
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 Pylons Project Waitress before 2.1.1 allows remote attackers to inject requests through a permissive proxy. The request parser passed unvalidated Content-Length and chunk-size strings to Python int(), while ChunkedReceiver discarded invalid chunk extensions. Exploitation requires a front-end proxy that interprets the malformed framing differently, allowing attacker-chosen HTTP messages to reach later application processing.

The record

CVE
CVE-2022-24761
Published
Mar 17, 2022
Updated
Apr 23, 2025
Vendor
Pylons Project
Product
Waitress
Classifications
CWE-444, CAPEC-33, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 17, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 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=< 2.1.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Pylons Project · Waitressversion=< 2.1.1

Published CVSS scores

5.0NISTAV:N/AC:L/Au:N/C:N/I:P/A:N
7.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
7.5NISTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
8.7GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA: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 exploitUnconfirmed

Weakness, pattern, technique

CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
CAPEC-33HTTP Request Smuggling
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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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