CVE-2023-22465 — http4s-core_2.13
HIGHCVE-2023-22465 is a high-severity (CVSS 7.5) Improper Input Validation vulnerability in org.http4s:http4s-core_2.13. 1 public exploit reference exists, so weaponization risk is real. A fix is available for org.http4s:http4s-core_2.13 — see the affected versions and patch details below.
Http4s has fatal error parsing User-Agent and Server headers
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-22465.
EPSS Exploitation Probability
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.
How urgent is this, really
CVE-2023-22465 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
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 moreReal-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
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.http4s:http4s-core_2.13 | ≥ 0.1.0&&< 0.21.34 | 0.21.34org.http4s:http4s-core_2.13:0.21.34 |
| ☕Maven | org.http4s:http4s-core_2.13 | ≥ 0.22.0&&< 0.22.15 | 0.22.15org.http4s:http4s-core_2.13:0.22.15 |
| ☕Maven | org.http4s:http4s-core_2.13 | ≥ 0.23.0&&< 0.23.17 | 0.23.17org.http4s:http4s-core_2.13:0.23.17 |
| ☕Maven | org.http4s:http4s-core_2.13 | ≥ 1.0.0-M1&&< 1.0.0-M38 | 1.0.0-M38org.http4s:http4s-core_2.13:1.0.0-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 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.http4s:http4s-core_2.13, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-22465 can be triaged on real exposure rather than presence alone.
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
Is CVE-2023-22465 in your dependencies?
O3 Security finds CVE-2023-22465 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.