CVE-2024-21631 is a medium-severity (CVSS 6.5) Improper Input Validation vulnerability in github.com/vapor/vapor. A fix is available for github.com/vapor/vapor — see the affected versions and patch details below.
Integer overflow in URI leading to potential host spoofing
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-2024-21631.
EPSS Exploitation Probability
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
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's vapor_urlparser_parse function uses uint16_t indexes when parsing a URI's components, which may cause integer overflows when parsing untrusted inputs.
This vulnerability does not affect Vapor directly but could impact applications relying on the URI type for validating user input.
The URI type is used in several places in Vapor. A developer may decide to use URI to represent a URL in their application (especially if that URL is then passed to the HTTP Client) and rely on its public properties and methods. However, URI may fail to properly parse a valid (albeit abnormally long) URL, due to string ranges being converted to 16-bit integers. An attacker may use this behaviour to trick the application into accepting a URL to an untrusted destination.
By padding the port number with zeros, an attacker can cause an integer overflow to occur when the URL authority is parsed and, as a result, spoof the host.
Impact
Users attempting to treat untrusted input as a URI are vulnerable to a host spoofing attack due to an integer overflow.
Workarounds
Validate user input before parsing as a URI or, if possible, use Foundation's URL and URLComponents utilities.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦SwiftURL | github.com/vapor/vapor | all versions | 4.90.0 |
Affected Products
vaporvaporDetection & 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 4.90.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-21631 is resolved across your whole dependency graph.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.
Frequently Asked Questions
Is CVE-2024-21631 in your dependencies?
Find it across SwiftURL, including transitive dependencies.