CVE-2023-22465

Http4s improperly parses User-Agent and Server headers

v0.21.x

val unsafe: Option[`User-Agent`] = req.headers.get(`User-Agent`)

v0.22.x, v0.23.x, v1.x

val unsafe: Option[`User-Agent`] = req.headers.get[`User-Agent`]
val alsoUnsafe: Option[`Server`] = req.headers.get[Server]

Workarounds

Use the weakly typed header interface

v0.21.x

val safe: Option[Header] = req.headers.get("User-Agent".ci)
// but don't do this
val unsafe = header.map(_.parsed) 

v0.22.x, v0.23.x, v1.x

val safe: Option[Header] = req.headers.get(ci"User-Agent")

The User-Agent and Server header parsers are susceptible to a fatal error on certain inputs. In http4s, modeled headers are lazily parsed, so this only applies to services that explicitly request these typed headers.

The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.

CVE-2023-22465 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.21.34, 0.22.15, 0.23.17, 1.0.0-M38); upgrading removes the vulnerable code path.

Kodem intelligence

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Fixes are released in 0.21.34, 0.22.15, 0.23.17, and 1.0.0-M38.

1. What is CVE-2023-22465? CVE-2023-22465 is a high-severity improper input validation vulnerability in org.http4s:http4s-core_2.13 (maven), affecting versions >= 0.1.0, < 0.21.34. It is fixed in 0.21.34, 0.22.15, 0.23.17, 1.0.0-M38. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
2. How severe is CVE-2023-22465? CVE-2023-22465 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2023-22465?
   • org.http4s:http4s-core_2.13 (maven) (versions >= 0.1.0, < 0.21.34)
   • org.http4s:http4s-core_2.10 (maven) (versions >= 0.1.0, <= 0.9.3)
   • org.http4s:http4s-core_2.11 (maven) (versions >= 0.1.0, <= 0.21.0-M1)
   • org.http4s:http4s-core_2.12 (maven) (versions >= 0.1.0, < 0.21.34)
   • org.http4s:http4s-core (maven) (versions >= 1.0.0-M1, <= 1.0.0-M30)
4. Is there a fix for CVE-2023-22465? Yes. CVE-2023-22465 is fixed in 0.21.34, 0.22.15, 0.23.17, 1.0.0-M38. Upgrade to this version or later.
5. Is CVE-2023-22465 exploitable, and should I be worried? Whether CVE-2023-22465 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-22465 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-22465?
   • Upgrade org.http4s:http4s-core_2.13 to 0.21.34 or later
   • Upgrade org.http4s:http4s-core_2.13 to 0.22.15 or later
   • Upgrade org.http4s:http4s-core_2.13 to 0.23.17 or later
   • Upgrade org.http4s:http4s-core_2.13 to 1.0.0-M38 or later
   • Upgrade org.http4s:http4s-core_2.12 to 0.21.34 or later
   • Upgrade org.http4s:http4s-core_2.12 to 0.22.15 or later
   • Upgrade org.http4s:http4s-core_2.12 to 0.23.17 or later