CVE-2023-0040
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedVersions 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThe Async HTTP Client library versions prior to 1.13.2 lack proper validation of HTTP header field values, allowing CRLF injection. Attackers can inject newline characters into header values to add arbitrary HTTP headers or split HTTP requests, manipulating how servers interpret requests.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 1.4.1>= 1.5.0, < 1.9.1>= 1.10.0, < 1.12.1>= 1.13.0, < 1.13.2CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify AsyncHttpClient version in useCheck your project's dependency management file (Maven pom.xml, Gradle build.gradle, or similar) for the async-http-client library version. Also inspect the JAR file manifest if deploying a compiled application.Affected if The installed version falls within any of these ranges: < 1.4.1, >= 1.5.0 and < 1.9.1, >= 1.10.0 and < 1.12.1, >= 1.13.0 and < 1.13.2
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Audit code that sets HTTP headersSearch your codebase for calls to async-http-client header-setting methods such as setHeader(), addHeader(), or building RequestBuilder objects. Identify any locations where user-supplied data (request parameters, form inputs, API payloads, or external API responses) flows into header field names or values.Affected if User-controllable data is passed to header field values without sanitization before being sent via AsyncHttpClient
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Check for CRLF character filteringInspect all code paths that pass data into HTTP headers via AsyncHttpClient. Look for any validation or filtering logic that removes or encodes carriage return (\r) and line feed (\n) characters from header values before they are used.Affected if No filtering of CR and LF characters exists in code that passes data to HTTP headers via AsyncHttpClient
You are affected if your AsyncHttpClient version is below 1.13.2 AND your application passes unsanitized user input into HTTP header values.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped1.4.11.9.11.12.1
Sanitize all user-supplied data before using it in HTTP header values by removing or encoding CR (\r) and LF (\n) characters, or use the patched version 1.13.2+ which implements proper validation.
1.13.2
- Identify the current version of Async HTTP Client in your project dependencies (check pom.xml, build.gradle, or similar dependency management file)
- Upgrade the Async HTTP Client dependency to version 1.13.2 or later
- For Maven: Update the dependency in pom.xml to: <groupId>org.asynchttpclient</groupId><artifactId>async-http-client</artifactId><version>2.12.3</version> (or the latest stable version)
- For Gradle: Update to: implementation 'org.asynchttpclient:async-http-client:2.12.3' (or the latest stable version)
- After upgrading, test your application to ensure HTTP header functionality still works correctly
- If you were previously sanitizing header values as a workaround, you can verify that the new version properly handles the validation internally
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-0040 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2023-0040 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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