GHSA-cf56-g6w6-pqq2
MEDIUMTwisted vulnerable to HTML injection in HTTP redirect body
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
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Description
Summary
The twisted.web.util.redirectTo function contains an HTML injection vulnerability. If application code allows an attacker to control the redirect URL this vulnerability may result in Reflected Cross-Site Scripting (XSS) in the redirect response HTML body.
Details
Twisted’s redirectTo function generates an HTTP 302 Redirect response. The response contains an HTML body, built for exceptional cases where the browser doesn’t properly handle the redirect, allowing the user to click a link, navigating them to the specified destination.
The function reflects the destination URL in the HTML body without any output encoding.
# https://github.com/twisted/twisted/blob/trunk/src/twisted/web/_template_util.py#L88
def redirectTo(URL: bytes, request: IRequest) -> bytes:
# ---snip---
content = b"""
<html>
<head>
<meta http-equiv=\"refresh\" content=\"0;URL=%(url)s\">
</head>
<body bgcolor=\"#FFFFFF\" text=\"#000000\">
<a href=\"%(url)s\">click here</a>
</body>
</html>
""" % {
b"url": URL
}
return content
If an attacker has full or partial control over redirect location due to an application bug, also known as an “Open Redirect”, they may inject arbitrary HTML into the response’s body, ultimately leading to an XSS attack.
It’s worth noting that the issue is known to maintainers and tracked with GitHub Issue#9839. The issue description, however, does not make any mention of exploitability and simply states: “…Browsers don't seem to actually render that page…”
PoC
The issue can be reproduced by running the following Twisted-based HTTP server locally:
from twisted.web import server, resource
from twisted.internet import reactor
from twisted.web.util import redirectTo
class Simple(resource.Resource):
isLeaf = True
def render_GET(self, request):
url = request.args[b'url'][0] # <-- open redirect
return redirectTo(url, request)
site = server.Site(Simple())
reactor.listenTCP(9009, site)
reactor.run()
Once running, navigate to the following URL: http://127.0.0.1:9009?url=ws://example.com/"><script>alert(document.location)</script>, and verify that the “alert” dialog was displayed.
Note: Due to the different ways browsers validate the redirect Location header, this attack is possible only in Firefox. All other tested browsers will display an error message to the user and will not render the HTML body.
Impact
If successfully exploited, the issue will allow malicious JavaScript to run in the context of the victim's session. This will in turn lead to unauthorized access/modification to victim's account and information associated with it, or allow for unauthorized operations to be performed within the context of the victim's session.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | twisted | all versions | 24.7.0rc1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for twisted. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update twisted to 24.7.0rc1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-cf56-g6w6-pqq2 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.
How O3 protects you
O3 pinpoints whether GHSA-cf56-g6w6-pqq2 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-cf56-g6w6-pqq2. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-cf56-g6w6-pqq2 in your dependencies?
O3 detects GHSA-cf56-g6w6-pqq2 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.