# CVE-2023-0040: Async HTTP Client has CRLF Injection vulnerability in HTTP request headers > Attackers can inject CRLF sequences into HTTP headers via untrusted data, causing request manipulation and logical errors in applications using the library. - **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 18 Jan 2023 - **Updated:** 3 Apr 2025 - **Also known as:** GHSA-v3r5-pjpm-mwgq ## What is CVE-2023-0040? CVE-2023-0040 is a high-severity vulnerability in Swift Project Async HTTP Client, published on 18 Jan 2023. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official 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. Weakness: CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component), CWE-93 (Improper Neutralization of CRLF Sequences) ## Which versions are affected by CVE-2023-0040? 8 open source packages ship an affected version, including github.com/swift-server/async-http-client. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `github.com/swift-server/async-http-client` | SwiftURL | All versions | 1.4.1 | | `github.com/swift-server/async-http-client` | SwiftURL | All versions | 1.4.1 | | `github.com/swift-server/async-http-client` | SwiftURL | From 1.10.0 | 1.12.1 | | `github.com/swift-server/async-http-client` | SwiftURL | From 1.10.0 | 1.12.1 | | `github.com/swift-server/async-http-client` | SwiftURL | From 1.13.0 | 1.13.2 | | `github.com/swift-server/async-http-client` | SwiftURL | From 1.13.0 | 1.13.2 | | `github.com/swift-server/async-http-client` | SwiftURL | From 1.5.0 | 1.9.1 | | `github.com/swift-server/async-http-client` | SwiftURL | From 1.5.0 | 1.9.1 | Products: Asynchttpclient Project Async-Http-Client. ## How do I fix CVE-2023-0040? Upgrade github.com/swift-server/async-http-client to a fixed version for your release line: 1.4.1, 1.12.1, 1.13.2 or 1.9.1. ## Is CVE-2023-0040 being exploited? There is no known exploitation of CVE-2023-0040 in the wild and no public exploit code. ## Other vulnerabilities in Swift Project Async HTTP Client - [CVE-2017-14063](https://insights.sbomify.com/CVE-2017-14063/): Improper Input Validation in async-http-client (high 7.5) - [CVE-2026-45300](https://insights.sbomify.com/CVE-2026-45300/): async-http-client: Cookie header not stripped on cross-origin redirect (high 7.4) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2023-0040 and fix it if it is affected. What it is: CVE-2023-0040 is a high-severity vulnerability in Swift Project Async HTTP Client, published on 18 Jan 2023. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2023-0040 in the wild and no public exploit code. Affected packages and fixed versions: - github.com/swift-server/async-http-client (SwiftURL): affected all versions; fixed in 1.4.1 - github.com/swift-server/async-http-client (SwiftURL): affected all versions; fixed in 1.4.1 - github.com/swift-server/async-http-client (SwiftURL): affected from 1.10.0; fixed in 1.12.1 - github.com/swift-server/async-http-client (SwiftURL): affected from 1.10.0; fixed in 1.12.1 - github.com/swift-server/async-http-client (SwiftURL): affected from 1.13.0; fixed in 1.13.2 - github.com/swift-server/async-http-client (SwiftURL): affected from 1.13.0; fixed in 1.13.2 - github.com/swift-server/async-http-client (SwiftURL): affected from 1.5.0; fixed in 1.9.1 - github.com/swift-server/async-http-client (SwiftURL): affected from 1.5.0; fixed in 1.9.1 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2023-0040/ (Markdown: https://insights.sbomify.com/CVE-2023-0040/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2023-0040 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-0040 - OSV: https://osv.dev/vulnerability/CVE-2023-0040 --- From sbomify Insights: https://insights.sbomify.com/CVE-2023-0040/ Summaries are generated and may contain mistakes; the official description above is the record.