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CVE-2022-39348 Moderate

Twisted vulnerable to NameVirtualHost Host header injection

When the host header does not match a configured host, `twisted.web.vhost.NameVirtualHost` will return a `NoResource` resource which renders the Host header unescaped into the 404 response allowing HTML and script injection. Example configuration: ```python from twisted.web.server import Site from twisted.web.vhost import NameVirtualHost from twisted.internet import reactor resource = NameVirtualHost() site = Site(resource) reactor.listenTCP(8080, site) reactor.run() ``` Output: ``` ❯ curl -H"Host:<h1>HELLO THERE</h1>" http://localhost:8080/ <html> <head><title>404 - No Such Resource</title></head> <body> <h1>No Such Resource</h1> <p>host b'<h1>hello there</h1>' not in vhost map</p> </body> </html> ``` This vulnerability was introduced in f49041bb67792506d85aeda9cf6157e92f8048f4 and first appeared in the 0.9.4 release.

Exploit probability 1.2%
Published July 7, 2026
Required by Not available
Last source change July 7, 2026

02 / AFFECTED SOFTWARE

Affected packages

Unknown Unknown

2 explicit affected versions

PyPI twisted

91 explicit affected versions

PyPI twisted

91 explicit affected versions

03 / CONNECTIONS

Connected vulnerabilities

04 / EVIDENCE

Source records

Open Source Vulnerabilities GHSA-vg46-2rrj-3647

When the host header does not match a configured host, `twisted.web.vhost.NameVirtualHost` will return a `NoResource` resource which renders the Host header unescaped into the 404 response allowing HTML and script injection. Example configuration: ```python from twisted.web.server import Site from twisted.web.vhost import NameVirtualHost from twisted.internet import reactor resource = NameVirtualHost() site = Site(resource) reactor.listenTCP(8080, site) reactor.run() ``` Output: ``` ❯ curl -H"Host:<h1>HELLO THERE</h1>" http://localhost:8080/ <html> <head><title>404 - No Such Resource</title></head> <body> <h1>No Such Resource</h1> <p>host b'<h1>hello there</h1>' not in vhost map</p> </body> </html> ``` This vulnerability was introduced in f49041bb67792506d85aeda9cf6157e92f8048f4 and first appeared in the 0.9.4 release.

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Open Source Vulnerabilities PYSEC-2026-1055

When the host header does not match a configured host, `twisted.web.vhost.NameVirtualHost` will return a `NoResource` resource which renders the Host header unescaped into the 404 response allowing HTML and script injection. Example configuration: ```python from twisted.web.server import Site from twisted.web.vhost import NameVirtualHost from twisted.internet import reactor resource = NameVirtualHost() site = Site(resource) reactor.listenTCP(8080, site) reactor.run() ``` Output: ``` ❯ curl -H"Host:<h1>HELLO THERE</h1>" http://localhost:8080/ <html> <head><title>404 - No Such Resource</title></head> <body> <h1>No Such Resource</h1> <p>host b'<h1>hello there</h1>' not in vhost map</p> </body> </html> ``` This vulnerability was introduced in f49041bb67792506d85aeda9cf6157e92f8048f4 and first appeared in the 0.9.4 release.

View original source
Open Source Vulnerabilities CVE-2022-39348

Twisted is an event-based framework for internet applications. Started with version 0.9.4, when the host header does not match a configured host `twisted.web.vhost.NameVirtualHost` will return a `NoResource` resource which renders the Host header unescaped into the 404 response allowing HTML and script injection. In practice this should be very difficult to exploit as being able to modify the Host header of a normal HTTP request implies that one is already in a privileged position. This issue was fixed in version 22.10.0rc1. There are no known workarounds.

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05 / REFERENCES

Further evidence