How severe is CVE-2023-22465?

CVE-2023-22465 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2023-22465?

CVE-2023-22465 affects the following packages: org.http4s:http4s-core_2.13 (Maven), org.http4s:http4s-core_2.13 (Maven), org.http4s:http4s-core_2.13 (Maven), org.http4s:http4s-core_2.13 (Maven), org.http4s:http4s-core_2.10 (Maven), org.http4s:http4s-core_2.11 (Maven), org.http4s:http4s-core_2.12 (Maven), org.http4s:http4s-core_2.12 (Maven), and 2 more. Ecosystems affected: Maven.

How do I fix CVE-2023-22465?

Update org.http4s:http4s-core_2.13 to 0.21.34 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-22465 is resolved across your whole dependency graph.

How do I detect CVE-2023-22465 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.http4s:http4s-core_2.13. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2023-22465 if there is no patch (or I can't update yet)?

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.

How does O3 Security protect against CVE-2023-22465?

O3 pinpoints whether CVE-2023-22465 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2023-22465 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2023-22465, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2023-22465?

CVE-2023-22465 has an EPSS (Exploit Prediction Scoring System) score of 0.8%, placing it in the 53th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was CVE-2023-22465 published, and has it been updated?

CVE-2023-22465 was published on January 4, 2023 and was last updated on April 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

CVE-2023-22465

HIGH

Http4s has fatal error parsing User-Agent and Server headers

Also known asGHSA-54w6-vxfh-fw7f

Published

Jan 4, 2023

Updated

Apr 10, 2026

Affected

10 pkgs

Patched

7 / 10

Exploits

1 known

EPSS Exploitation Probability

via FIRST.org ↗

0.8%probability of exploitation in next 30 days

Lower Risk53th percentile+0.51%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

10 pkgs affected

☕org.http4s:http4s-core_2.13☕org.http4s:http4s-core_2.13☕org.http4s:http4s-core_2.13☕org.http4s:http4s-core_2.13☕org.http4s:http4s-core_2.10☕org.http4s:http4s-core_2.11☕org.http4s:http4s-core_2.12☕org.http4s:http4s-core_2.12+2 more

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Http4s is a Scala interface for HTTP services. Starting with version 0.1.0 and prior to versions 0.21.34, 0.22.15, 0.23.17, and 1.0.0-M38, 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. Fixes are released in 0.21.34, 0.22.15, 0.23.17, and 1.0.0-M38. As a workaround, use the weakly typed header interface.

Affected Packages

10 total 7 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.http4s:http4s-core_2.13`	≥ 0.1.0&&< 0.21.34	0.21.34
☕Maven	`org.http4s:http4s-core_2.13`	≥ 0.22.0&&< 0.22.15	0.22.15
☕Maven	`org.http4s:http4s-core_2.13`	≥ 0.23.0&&< 0.23.17	0.23.17
☕Maven	`org.http4s:http4s-core_2.13`	≥ 1.0.0-M1&&< 1.0.0-M38	1.0.0-M38
☕Maven	`org.http4s:http4s-core_2.10`	≥ 0.1.0	No fix
☕Maven	`org.http4s:http4s-core_2.11`	≥ 0.1.0	No fix

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Http4s is a Scala interface for HTTP services. Starting with version 0.1…

github.comNVDJan 2023

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.http4s:http4s-core_2.13. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.http4s:http4s-core_2.13 to 0.21.34 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-22465 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.
How O3 protects you
O3 pinpoints whether CVE-2023-22465 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2023-22465. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

Http4s is a Scala interface for HTTP services. Starting with version 0.1.0 and prior to versions 0.21.34, 0.22.15, 0.23.17, and 1.0.0-M38, 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. Fixes are released in 0.21.34, 0.22.15, 0.23.17, and 1.0.0-M38. As a workaround, use the weakly typed header interface.

O3 Security · Impact-Aware SCA

Is CVE-2023-22465 in your dependencies?

O3 detects CVE-2023-22465 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works