GHSA-qvxg-wjxc-r4gg is a high-severity (CVSS 7.5) CWE-120 vulnerability in github.com/vapor/vapor. 1 public exploit reference exists, so weaponization risk is real. A fix is available for github.com/vapor/vapor — see the affected versions and patch details below.
Vapor vulnerable to denial of service in URLEncodedFormDecoder
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.
How urgent is this, really
GHSA-qvxg-wjxc-r4gg plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/vapor/vaporReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects SwiftURL packages — download data is not available via public APIs for these ecosystems.
Description
Vapor is an HTTP web framework for Swift. Vapor versions earlier than 4.61.1 are vulnerable to a denial of service in the URLEncodedFormDecoder.
Impact
When using automatic content decoding, e.g.
app.post("foo") { request -> String in
let foo = try request.content.decode(Foo.self)
return "\(foo)"
}
An attacker can craft a request body that can make the server crash with the following request:
curl -d "array[_0][0][array][_0][0][array]$(for f in $(seq 1100); do echo -n '[_0][0][array]'; done)[string][_0]=hello%20world" http://localhost:8080/foo
The issue is unbounded, attacker controlled stack growth which will at some point lead to a stack overflow.
Patches
Fixed in 4.61.1
Workarounds
If you don't need to decode Form URL Encoded data, you can disable the ContentConfiguration so it won't be used. E.g. in configure.swift
var contentConfig = ContentConfiguration()
contentConfig.use(encoder: JSONEncoder.custom(dates: .iso8601), for: .json)
contentConfig.use(decoder: JSONDecoder.custom(dates: .iso8601), for: .json)
contentConfig.use(encoder: JSONEncoder.custom(dates: .iso8601), for: .jsonAPI)
contentConfig.use(decoder: JSONDecoder.custom(dates: .iso8601), for: .jsonAPI)
ContentConfiguration.global = contentConfig
For more information
If you have any questions or comments about this advisory:
- Open an issue in the Vapor repo
- Ask in Vapor Discord
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦SwiftURL | github.com/vapor/vapor | all versions | 4.61.1 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/vapor/vapor, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/vapor/vapor to 4.61.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-qvxg-wjxc-r4gg 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-qvxg-wjxc-r4gg can be triaged on real exposure rather than presence alone.
Tailored to GHSA-qvxg-wjxc-r4gg. 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-qvxg-wjxc-r4gg in your dependencies?
O3 Security finds GHSA-qvxg-wjxc-r4gg across SwiftURL dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.