CVE-2023-0040 is a high-severity (CVSS 7.5) CWE-93 vulnerability in github.com/swift-server/async-http-client. A fix is available for github.com/swift-server/async-http-client — see the affected versions and patch details below.
Async HTTP Client has CRLF Injection vulnerability in HTTP request headers
Exploitation Status
No confirmed exploitation observed yet
- 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-2023-0040.
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/swift-server/async-http-client📦github.com/swift-server/async-http-client📦github.com/swift-server/async-http-client📦github.com/swift-server/async-http-clientReal-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
Versions of Async HTTP Client prior to 1.13.2 are vulnerable to a form of targeted request manipulation called CRLF injection. This vulnerability was the result of insufficient validation of HTTP header field values before sending them to the network. Users are vulnerable if they pass untrusted data into HTTP header field values without prior sanitisation. Common use-cases here might be to place usernames from a database into HTTP header fields. This vulnerability allows attackers to inject new HTTP header fields, or entirely new requests, into the data stream. This can cause requests to be understood very differently by the remote server than was intended. In general, this is unlikely to result in data disclosure, but it can result in a number of logical errors and other misbehaviours.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦SwiftURL | github.com/swift-server/async-http-client | ≥ 1.13.0&&< 1.13.2 | 1.13.2 |
| 📦SwiftURL | github.com/swift-server/async-http-client | ≥ 1.10.0&&< 1.12.1 | 1.12.1 |
| 📦SwiftURL | github.com/swift-server/async-http-client | ≥ 1.5.0&&< 1.9.1 | 1.9.1 |
| 📦SwiftURL | github.com/swift-server/async-http-client | all versions | 1.4.1 |
Affected Products
async-http-clientasynchttpclient_projectDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/swift-server/async-http-client, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/swift-server/async-http-client to 1.13.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-0040 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.
Frequently Asked Questions
Is CVE-2023-0040 in your dependencies?
Find it across SwiftURL, including transitive dependencies.