http4k has a potential XXE (XML External Entity Injection) vulnerability

Summary

http4k is a functional toolkit for Kotlin HTTP applications. Prior to version 6.50.0.0, there is a potential XXE (XML External Entity Injection) vulnerability when http4k handling malicious XML contents within requests, which might allow attackers to read local sensitive information on server, trigger Server-side Request Forgery and even execute code under some circumstances. The original fix shipped in v5.41.0.0 / v4.50.0.0 closed the documented external-entity attack class (SSRF, local-file disclosure, code execution) by setting `ACCESS_EXTERNAL_DTD=""`, `ACCESS_EXTERNAL_SCHEMA=""`, and `isExpandEntityReferences=false` on the default `DocumentBuilderFactory`. A residual gap remained: the parser still accepted documents containing `<!DOCTYPE>` declarations even though external entity resolution was blocked. This left open billion-laughs-style internal entity expansion DoS attacks against any application using `Body.xml()` or `Document.asXmlDocument()` on untrusted XML. v6.50.0.0 closes this residual by adding `disallow-doctype-decl=true` and `FEATURE_SECURE_PROCESSING=true` to `defaultXmlParsingConfig`. Any document containing a `<!DOCTYPE>` is now rejected at parse time.

Timeline

1. Dec 12, 2024, 6:56 PM UTCCVE published
2. Dec 13, 2024, 2:52 PM UTCCISA SSVC assessment

   Exploitation: poc · Automatable: yes · Technical impact: total

3. Jun 9, 2026, 10:42 AM UTCRecord last updated

Affected versions

• http4k http4k

  fixed in 6.50.0.0

• org.http4k:http4k-format-xmlMaven

  fixed in 6.50.0.0

References 4