How severe is CVE-2022-24761?

CVE-2022-24761 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2022-24761?

CVE-2022-24761 affects the following packages: waitress (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2022-24761?

Update waitress to 2.1.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-24761 is resolved across your whole dependency graph.

How do I detect CVE-2022-24761 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for waitress, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2022-24761 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2022-24761 actively exploited in the wild?

No public exploit code has been indexed for CVE-2022-24761 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2022-24761?

CVE-2022-24761 has an EPSS (Exploit Prediction Scoring System) score of 1.8%, placing it in the 78th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2022-24761?

CVE-2022-24761 is classified as CWE-444 (CWE-444). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2022-24761 published, and has it been updated?

CVE-2022-24761 was published on March 17, 2022 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍

🐍 PyPI

Not in CISA KEV

HIGH severity

CVE-2022-24761 — waitress

HIGHFix: Pylons/waitress@9e0b8c8

CVE-2022-24761 is a high-severity (CVSS 7.5) CWE-444 vulnerability in waitress. A fix is available for waitress — see the affected versions and patch details below.

HTTP Request Smuggling in waitress

Also known asGHSA-4f7p-27jc-3c36PYSEC-2022-169

Published

Mar 17, 2022

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2022-24761.

EPSS Exploitation Probability

via FIRST.org ↗

1.8%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs78th percentile — riskier than 78% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

🐍waitress

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Impact

When using Waitress behind a proxy that does not properly validate the incoming HTTP request matches the RFC7230 standard, Waitress and the frontend proxy may disagree on where one request starts and where it ends.

This would allow requests to be smuggled via the front-end proxy to waitress and later behavior.

There are two classes of vulnerability that may lead to request smuggling that are addressed by this advisory:

The use of Python's int() to parse strings into integers, leading to +10 to be parsed as 10, or 0x01 to be parsed as 1, where as the standard specifies that the string should contain only digits or hex digits.
Waitress does not support chunk extensions, however it was discarding them without validating that they did not contain illegal characters

Patches

This has been fixed in Waitress 2.1.1

Workarounds

When deploying a proxy in front of waitress, turning on any and all functionality to make sure that the request matches the RFC7230 standard. Certain proxy servers may not have this functionality though and users are encouraged to upgrade to the latest version of waitress instead.

References

https://portswigger.net/research/http-desync-attacks-request-smuggling-reborn

For more information

If you have any questions or comments about this advisory:

Open an issue in the Github issue tracker (if not security related/sensitive)
Email us at [email protected] (If security related or sensitive)

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`waitress`	all versions	2.1.1`pip install --upgrade 'waitress==2.1.1'`

Affected Products

2 products · 2 configurations

Application

waitressagendaless

< 2.1.1

range

debian linuxdebian

1 version

9.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for waitress, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update waitress to 2.1.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-24761 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

Product	Fixed in	Advisory
Red Hat OpenStack Platform 13.0 - ELS	`python-waitress-0:1.4.4-2.el7ost`	RHSA-2022:1264
Red Hat OpenStack Platform 16.1	`python-waitress-0:2.0.0-1.el8ost`	RHSA-2022:1254
Red Hat OpenStack Platform 16.2	`python-waitress-0:2.0.0-1.el8ost`	RHSA-2022:1253

Frequently Asked Questions

### Impact When using Waitress behind a proxy that does not properly validate the incoming HTTP request matches the RFC7230 standard, Waitress and the frontend proxy may disagree on where one request starts and where it ends. This would allow requests to be smuggled via the front-end proxy to waitress and later behavior. There are two classes of vulnerability that may lead to request smuggling that are addressed by this advisory: - The use of Python's `int()` to parse strings into integers, leading to `+10` to be parsed as `10`, or `0x01` to be parsed as `1`, where as the standard specifie